issues: 834641104

What happened:

I could not open the test dataset on master. It's a bit strange that this is not picked up by the tests, so probably something to do with the environment I have (I just updated all packages).

@alexamici @aurghs does that tell you anything?

I can also try to figure it out.

Minimal Complete Verifiable Example:

calling open_dataset with "" is enough to trigger the error:

python import xarray as xr air = xr.open_dataset("")

Anything else we need to know?:

And the traceback:

```python-traceback --------------------------------------------------------------------------- AttributeError Traceback (most recent call last) ~/conda/envs/xarray_dev/lib/python3.8/site-packages/pkg_resources/__init__.py in resolve(self) 2479 try: -> 2480 return functools.reduce(getattr, self.attrs, module) 2481 except AttributeError as exc: AttributeError: module 'xarray.backends.cfgrib_' has no attribute 'cfgrib_backend' The above exception was the direct cause of the following exception: ImportError Traceback (most recent call last) <ipython-input-2-16bed41155fa> in <module> ----> 1 air = xr.tutorial.open_dataset("air_temperature") ~/code/xarray/xarray/tutorial.py in open_dataset(name, cache, cache_dir, github_url, branch, **kws) 93 raise OSError(msg) 94 ---> 95 ds = _open_dataset(localfile, **kws) 96 97 if not cache: ~/code/xarray/xarray/backends/api.py in open_dataset(filename_or_obj, engine, chunks, cache, decode_cf, mask_and_scale, decode_times, decode_timedelta, use_cftime, concat_characters, decode_coords, drop_variables, backend_kwargs, *args, **kwargs) 491 492 if engine is None: --> 493 engine = plugins.guess_engine(filename_or_obj) 494 495 backend = plugins.get_backend(engine) ~/code/xarray/xarray/backends/plugins.py in guess_engine(store_spec) 99 100 def guess_engine(store_spec): --> 101 engines = list_engines() 102 103 for engine, backend in engines.items(): ~/code/xarray/xarray/backends/plugins.py in list_engines() 95 def list_engines(): 96 pkg_entrypoints = pkg_resources.iter_entry_points("xarray.backends") ---> 97 return build_engines(pkg_entrypoints) 98 99 ~/code/xarray/xarray/backends/plugins.py in build_engines(pkg_entrypoints) 82 backend_entrypoints = BACKEND_ENTRYPOINTS.copy() 83 pkg_entrypoints = remove_duplicates(pkg_entrypoints) ---> 84 external_backend_entrypoints = backends_dict_from_pkg(pkg_entrypoints) 85 backend_entrypoints.update(external_backend_entrypoints) 86 backend_entrypoints = sort_backends(backend_entrypoints) ~/code/xarray/xarray/backends/plugins.py in backends_dict_from_pkg(pkg_entrypoints) 56 for pkg_ep in pkg_entrypoints: 57 name = pkg_ep.name ---> 58 backend = pkg_ep.load() 59 backend_entrypoints[name] = backend 60 return backend_entrypoints ~/conda/envs/xarray_dev/lib/python3.8/site-packages/pkg_resources/__init__.py in load(self, require, *args, **kwargs) 2470 if require: 2471 self.require(*args, **kwargs) -> 2472 return self.resolve() 2473 2474 def resolve(self): ~/conda/envs/xarray_dev/lib/python3.8/site-packages/pkg_resources/__init__.py in resolve(self) 2480 return functools.reduce(getattr, self.attrs, module) 2481 except AttributeError as exc: -> 2482 raise ImportError(str(exc)) from exc 2483 2484 def require(self, env=None, installer=None): ImportError: module 'xarray.backends.cfgrib_' has no attribute 'cfgrib_backend' ```

Environment:

Output of <tt>xr.show_versions()</tt>

``` INSTALLED VERSIONS ------------------ commit: a6f51c680f4e4c3ed5101b9c1111f0b94d28a781 python: 3.8.6 | packaged by conda-forge | (default, Jan 25 2021, 23:21:18) [GCC 9.3.0] python-bits: 64 OS: Linux OS-release: 5.4.0-67-generic machine: x86_64 processor: x86_64 byteorder: little LC_ALL: None LANG: en_US.UTF-8 LOCALE: en_US.UTF-8 libhdf5: 1.10.6 libnetcdf: 4.7.4 xarray: 0.16.2.dev111+g0d93c4f9.d20201219 pandas: 1.2.3 numpy: 1.20.1 scipy: 1.6.1 netCDF4: 1.5.6 pydap: installed h5netcdf: 0.10.0 h5py: 3.1.0 Nio: None zarr: 2.6.1 cftime: 1.4.1 nc_time_axis: 1.2.0 PseudoNetCDF: installed rasterio: 1.2.1 cfgrib: 0.9.8.5 iris: 2.4.0 bottleneck: 1.3.2 dask: 2021.03.0 distributed: 2021.03.0 matplotlib: 3.3.4 cartopy: 0.18.0 seaborn: 0.11.1 numbagg: installed pint: 0.16.1 setuptools: 49.6.0.post20210108 pip: 21.0.1 conda: None pytest: 6.2.2 IPython: 7.21.0 sphinx: None ```

and my conda list:

``` # packages in environment at /home/mathause/conda/envs/xarray_dev: # # Name Version Build Channel _libgcc_mutex 0.1 conda_forge conda-forge _openmp_mutex 4.5 1_gnu conda-forge affine 2.3.0 py_0 conda-forge antlr-python-runtime 4.7.2 py38h578d9bd_1002 conda-forge apipkg 1.5 py_0 conda-forge appdirs 1.4.4 pyh9f0ad1d_0 conda-forge asciitree 0.3.3 py_2 conda-forge attrs 20.3.0 pyhd3deb0d_0 conda-forge backcall 0.2.0 pyh9f0ad1d_0 conda-forge backports 1.0 py_2 conda-forge backports.functools_lru_cache 1.6.1 py_0 conda-forge beautifulsoup4 4.9.3 pyhb0f4dca_0 conda-forge black 20.8b1 py_1 conda-forge bokeh 2.3.0 py38h578d9bd_0 conda-forge boost-cpp 1.72.0 h9d3c048_4 conda-forge boto3 1.17.30 pyhd8ed1ab_0 conda-forge botocore 1.20.30 pyhd8ed1ab_0 conda-forge bottleneck 1.3.2 py38h5c078b8_3 conda-forge brotlipy 0.7.0 py38h497a2fe_1001 conda-forge bzip2 1.0.8 h7f98852_4 conda-forge c-ares 1.17.1 h7f98852_1 conda-forge ca-certificates 2020.12.5 ha878542_0 conda-forge cached-property 1.5.2 hd8ed1ab_1 conda-forge cached_property 1.5.2 pyha770c72_1 conda-forge cairo 1.16.0 h7979940_1007 conda-forge cartopy 0.18.0 py38hab71064_13 conda-forge cdat_info 8.2.1 pyh9f0ad1d_1 conda-forge cdms2 3.1.5 pypi_0 pypi cdtime 3.1.4 py38h49bcaf2_2 conda-forge certifi 2020.12.5 py38h578d9bd_1 conda-forge cf-units 2.1.4 py38hab2c0dc_2 conda-forge cffi 1.14.5 py38ha65f79e_0 conda-forge cfgrib 0.9.8.5 pyhd8ed1ab_0 conda-forge cfgv 3.2.0 py_0 conda-forge cfitsio 3.470 hb418390_7 conda-forge cftime 1.4.1 py38h5c078b8_0 conda-forge chardet 4.0.0 py38h578d9bd_1 conda-forge click 7.1.2 pyh9f0ad1d_0 conda-forge click-plugins 1.1.1 py_0 conda-forge cligj 0.7.1 pyhd8ed1ab_0 conda-forge cloudpickle 1.6.0 py_0 conda-forge coverage 5.5 py38h497a2fe_0 conda-forge coveralls 3.0.1 pyhd8ed1ab_0 conda-forge cryptography 3.4.6 py38ha5dfef3_0 conda-forge curl 7.75.0 h979ede3_0 conda-forge cycler 0.10.0 py_2 conda-forge cytoolz 0.11.0 py38h497a2fe_3 conda-forge dask 2021.3.0 pyhd8ed1ab_0 conda-forge dask-core 2021.3.0 pyhd8ed1ab_0 conda-forge dataclasses 0.8 pyhc8e2a94_1 conda-forge dbus 1.13.6 hfdff14a_1 conda-forge decorator 4.4.2 py_0 conda-forge distarray 2.12.2 py_1 conda-forge distlib 0.3.1 pyh9f0ad1d_0 conda-forge distributed 2021.3.0 py38h578d9bd_0 conda-forge docopt 0.6.2 py_1 conda-forge eccodes 2.20.0 ha0e6eb6_0 conda-forge editdistance 0.5.3 py38h709712a_3 conda-forge esmf 8.0.1 mpi_mpich_h3cbecb6_102 conda-forge esmpy 8.0.1 mpi_mpich_py38h6f0bf2d_102 conda-forge execnet 1.8.0 pyh44b312d_0 conda-forge expat 2.2.10 h9c3ff4c_0 conda-forge fasteners 0.14.1 py_3 conda-forge filelock 3.0.12 pyh9f0ad1d_0 conda-forge flake8 3.9.0 pyhd8ed1ab_0 conda-forge fontconfig 2.13.1 hba837de_1004 conda-forge freetype 2.10.4 h0708190_1 conda-forge freexl 1.0.6 h7f98852_0 conda-forge fsspec 0.8.7 pyhd8ed1ab_0 conda-forge future 0.18.2 py38h578d9bd_3 conda-forge g2clib 1.6.0 hf3f1b0b_9 conda-forge geos 3.9.1 h9c3ff4c_2 conda-forge geotiff 1.6.0 h11d48b3_4 conda-forge gettext 0.19.8.1 h0b5b191_1005 conda-forge giflib 5.2.1 h516909a_2 conda-forge glib 2.66.7 h9c3ff4c_1 conda-forge glib-tools 2.66.7 h9c3ff4c_1 conda-forge gprof2dot 2019.11.30 py_0 conda-forge gst-plugins-base 1.18.4 h29181c9_0 conda-forge gstreamer 1.18.4 h76c114f_0 conda-forge h5netcdf 0.10.0 pyhd8ed1ab_0 conda-forge h5py 3.1.0 nompi_py38hafa665b_100 conda-forge hdf4 4.2.13 h10796ff_1004 conda-forge hdf5 1.10.6 mpi_mpich_h996c276_1014 conda-forge heapdict 1.0.1 py_0 conda-forge hypothesis 6.8.1 pyhd8ed1ab_0 conda-forge icu 68.1 h58526e2_0 conda-forge identify 2.1.3 pyhd8ed1ab_0 conda-forge idna 2.10 pyh9f0ad1d_0 conda-forge importlib-metadata 3.7.3 py38h578d9bd_0 conda-forge importlib_metadata 3.7.3 hd8ed1ab_0 conda-forge importlib_resources 5.1.2 py38h578d9bd_0 conda-forge iniconfig 1.1.1 pyh9f0ad1d_0 conda-forge ipython 7.21.0 py38h81c977d_0 conda-forge ipython_genutils 0.2.0 py_1 conda-forge iris 2.4.0 py38h578d9bd_1 conda-forge isort 5.7.0 pyhd8ed1ab_0 conda-forge jasper 1.900.1 h07fcdf6_1006 conda-forge jedi 0.18.0 py38h578d9bd_2 conda-forge jinja2 2.11.3 pyh44b312d_0 conda-forge jmespath 0.10.0 pyh9f0ad1d_0 conda-forge jpeg 9d h516909a_0 conda-forge json-c 0.15 h98cffda_0 conda-forge jsonschema 3.2.0 py38h32f6830_1 conda-forge jupyter_core 4.7.1 py38h578d9bd_0 conda-forge kealib 1.4.14 hcc255d8_2 conda-forge kiwisolver 1.3.1 py38h1fd1430_1 conda-forge krb5 1.17.2 h926e7f8_0 conda-forge lazy-object-proxy 1.5.2 py38h497a2fe_1 conda-forge lcms2 2.12 hddcbb42_0 conda-forge ld_impl_linux-64 2.35.1 hea4e1c9_2 conda-forge libaec 1.0.4 he1b5a44_1 conda-forge libblas 3.8.0 17_openblas conda-forge libcblas 3.8.0 17_openblas conda-forge libcdms 3.1.2 h981a4fd_113 conda-forge libcf 1.0.3 py38h88b7cc0_109 conda-forge libclang 11.1.0 default_ha53f305_0 conda-forge libcst 0.3.17 py38h578d9bd_0 conda-forge libcurl 7.75.0 hc4aaa36_0 conda-forge libdap4 3.20.6 hd7c4107_1 conda-forge libdrs 3.1.2 h7918d09_113 conda-forge libdrs_f 3.1.2 h5026c31_111 conda-forge libedit 3.1.20191231 he28a2e2_2 conda-forge libev 4.33 h516909a_1 conda-forge libevent 2.1.10 hcdb4288_3 conda-forge libffi 3.3 h58526e2_2 conda-forge libgcc-ng 9.3.0 h2828fa1_18 conda-forge libgdal 3.2.1 h38ff51b_7 conda-forge libgfortran-ng 9.3.0 hff62375_18 conda-forge libgfortran5 9.3.0 hff62375_18 conda-forge libglib 2.66.7 h3e27bee_1 conda-forge libgomp 9.3.0 h2828fa1_18 conda-forge libiconv 1.16 h516909a_0 conda-forge libkml 1.3.0 hd79254b_1012 conda-forge liblapack 3.8.0 17_openblas conda-forge libllvm10 10.0.1 he513fc3_3 conda-forge libllvm11 11.1.0 hf817b99_0 conda-forge libnetcdf 4.7.4 mpi_mpich_hdef422e_7 conda-forge libnghttp2 1.43.0 h812cca2_0 conda-forge libopenblas 0.3.10 pthreads_h4812303_5 conda-forge libpng 1.6.37 hed695b0_2 conda-forge libpq 13.1 hfd2b0eb_2 conda-forge librttopo 1.1.0 h1185371_6 conda-forge libspatialite 5.0.1 he52d314_3 conda-forge libssh2 1.9.0 ha56f1ee_6 conda-forge libstdcxx-ng 9.3.0 h6de172a_18 conda-forge libtiff 4.2.0 hdc55705_0 conda-forge libuuid 2.32.1 h14c3975_1000 conda-forge libwebp-base 1.2.0 h7f98852_2 conda-forge libxcb 1.13 h7f98852_1003 conda-forge libxkbcommon 1.0.3 he3ba5ed_0 conda-forge libxml2 2.9.10 h72842e0_3 conda-forge libxslt 1.1.33 h15afd5d_2 conda-forge line_profiler 3.1.0 py38h82cb98a_1 conda-forge llvmlite 0.36.0 py38h4630a5e_0 conda-forge locket 0.2.0 py_2 conda-forge lxml 4.6.2 py38hf1fe3a4_1 conda-forge lz4-c 1.9.3 h9c3ff4c_0 conda-forge markupsafe 1.1.1 py38h497a2fe_3 conda-forge matplotlib 3.3.4 py38h578d9bd_0 conda-forge matplotlib-base 3.3.4 py38h0efea84_0 conda-forge mccabe 0.6.1 py_1 conda-forge mechanicalsoup 1.0.0 pyhd8ed1ab_0 conda-forge monkeytype 20.5.0 pyh516909a_0 conda-forge monotonic 1.5 py_0 conda-forge more-itertools 8.7.0 pyhd8ed1ab_0 conda-forge mpi 1.0 mpich conda-forge mpi4py 3.0.3 py38he865349_5 conda-forge mpich 3.4.1 h846660c_104 conda-forge msgpack-python 1.0.2 py38h1fd1430_1 conda-forge mypy 0.812 pyhd8ed1ab_0 conda-forge mypy_extensions 0.4.3 py38h578d9bd_3 conda-forge mysql-common 8.0.23 ha770c72_1 conda-forge mysql-libs 8.0.23 h935591d_1 conda-forge nbformat 5.1.2 pyhd8ed1ab_1 conda-forge nc-time-axis 1.2.0 py_1 conda-forge ncurses 6.2 h58526e2_4 conda-forge netcdf-fortran 4.5.3 mpi_mpich_h7ad8bfe_1 conda-forge netcdf4 1.5.6 nompi_py38h1cdf482_100 conda-forge nodeenv 1.5.0 pyh9f0ad1d_0 conda-forge nspr 4.30 h9c3ff4c_0 conda-forge nss 3.62 hb5efdd6_0 conda-forge numba 0.53.0 py38h5e62926_1 conda-forge numbagg 0.1 pypi_0 pypi numcodecs 0.7.3 py38h709712a_0 conda-forge numpy 1.20.1 py38h18fd61f_0 conda-forge olefile 0.46 pyh9f0ad1d_1 conda-forge openblas 0.3.10 pthreads_h04b7a96_5 conda-forge openjpeg 2.4.0 hf7af979_0 conda-forge openssl 1.1.1j h7f98852_0 conda-forge packaging 20.9 pyh44b312d_0 conda-forge pandas 1.2.3 py38h51da96c_0 conda-forge parso 0.8.1 pyhd8ed1ab_0 conda-forge partd 1.1.0 py_0 conda-forge pathspec 0.8.1 pyhd3deb0d_0 conda-forge patsy 0.5.1 py_0 conda-forge pcre 8.44 he1b5a44_0 conda-forge pexpect 4.8.0 py38h32f6830_1 conda-forge pickleshare 0.7.5 py38h32f6830_1002 conda-forge pillow 8.1.2 py38ha0e1e83_0 conda-forge pint 0.16.1 py_0 conda-forge pip 21.0.1 pyhd8ed1ab_0 conda-forge pixman 0.40.0 h36c2ea0_0 conda-forge pluggy 0.13.1 py38h578d9bd_4 conda-forge poppler 0.89.0 h2de54a5_5 conda-forge poppler-data 0.4.10 0 conda-forge postgresql 13.1 h6303168_2 conda-forge pre-commit 2.11.1 py38h578d9bd_0 conda-forge proj 7.2.0 h277dcde_2 conda-forge prompt-toolkit 3.0.17 pyha770c72_0 conda-forge pseudonetcdf 3.1.0 py_1 conda-forge psutil 5.8.0 py38h497a2fe_1 conda-forge pthread-stubs 0.4 h36c2ea0_1001 conda-forge ptyprocess 0.7.0 pyhd3deb0d_0 conda-forge py 1.10.0 pyhd3deb0d_0 conda-forge pycodestyle 2.7.0 pyhd8ed1ab_0 conda-forge pycparser 2.20 pyh9f0ad1d_2 conda-forge pydap 3.2.2 py38_1000 conda-forge pyflakes 2.3.0 pyhd8ed1ab_0 conda-forge pygments 2.8.1 pyhd8ed1ab_0 conda-forge pyke 1.1.1 py38h578d9bd_1003 conda-forge pyopenssl 20.0.1 pyhd8ed1ab_0 conda-forge pyparsing 2.4.7 pyh9f0ad1d_0 conda-forge pyqt 5.12.3 py38h578d9bd_7 conda-forge pyqt-impl 5.12.3 py38h7400c14_7 conda-forge pyqt5-sip 4.19.18 py38h709712a_7 conda-forge pyqtchart 5.12 py38h7400c14_7 conda-forge pyqtwebengine 5.12.1 py38h7400c14_7 conda-forge pyrsistent 0.17.3 py38h497a2fe_2 conda-forge pyshp 2.1.3 pyh44b312d_0 conda-forge pysocks 1.7.1 py38h578d9bd_3 conda-forge pytest 6.2.2 py38h578d9bd_0 conda-forge pytest-cov 2.11.1 pyh44b312d_0 conda-forge pytest-env 0.6.2 py_0 conda-forge pytest-forked 1.3.0 pyhd3deb0d_0 conda-forge pytest-profiling 1.7.0 py_1 conda-forge pytest-xdist 2.2.1 pyhd8ed1ab_0 conda-forge python 3.8.6 hffdb5ce_5_cpython conda-forge python-dateutil 2.8.1 py_0 conda-forge python-xxhash 2.0.0 py38h497a2fe_1 conda-forge python_abi 3.8 1_cp38 conda-forge pytz 2021.1 pyhd8ed1ab_0 conda-forge pyyaml 5.4.1 py38h497a2fe_0 conda-forge qt 5.12.9 hda022c4_4 conda-forge rasterio 1.2.1 py38h57accd2_2 conda-forge readline 8.0 he28a2e2_2 conda-forge regex 2020.11.13 py38h497a2fe_1 conda-forge regrid2 3.1.5 pypi_0 pypi requests 2.25.1 pyhd3deb0d_0 conda-forge s3transfer 0.3.4 pyhd8ed1ab_0 conda-forge scipy 1.6.1 py38hb2138dd_0 conda-forge seaborn 0.11.1 ha770c72_0 conda-forge seaborn-base 0.11.1 pyhd8ed1ab_1 conda-forge setuptools 49.6.0 py38h578d9bd_3 conda-forge shapely 1.7.1 py38h4fc1155_4 conda-forge six 1.15.0 pyh9f0ad1d_0 conda-forge snuggs 1.4.7 py_0 conda-forge sortedcontainers 2.3.0 pyhd8ed1ab_0 conda-forge soupsieve 2.0.1 py38h32f6830_0 conda-forge sparse 0.11.2 py_0 conda-forge sqlite 3.34.0 h74cdb3f_0 conda-forge statsmodels 0.12.2 py38h5c078b8_0 conda-forge tblib 1.6.0 py_0 conda-forge tiledb 2.2.5 h91fcb0e_0 conda-forge tk 8.6.10 hed695b0_1 conda-forge toml 0.10.2 pyhd8ed1ab_0 conda-forge toolz 0.11.1 py_0 conda-forge tornado 6.1 py38h497a2fe_1 conda-forge traitlets 5.0.5 py_0 conda-forge typed-ast 1.4.2 py38h497a2fe_0 conda-forge typing_extensions 3.7.4.3 py_0 conda-forge typing_inspect 0.6.0 pyh9f0ad1d_0 conda-forge tzcode 2021a h7f98852_1 conda-forge tzdata 2021a he74cb21_0 conda-forge udunits2 2.2.27.27 h360fe7b_0 conda-forge urllib3 1.26.4 pyhd8ed1ab_0 conda-forge virtualenv 20.4.3 py38h578d9bd_0 conda-forge wcwidth 0.2.5 pyh9f0ad1d_2 conda-forge webob 1.8.6 py_0 conda-forge wheel 0.36.2 pyhd3deb0d_0 conda-forge xarray 0.16.2.dev111+g0d93c4f9.d20201219 dev_0 <develop> xerces-c 3.2.3 h9d8b166_2 conda-forge xorg-kbproto 1.0.7 h14c3975_1002 conda-forge xorg-libice 1.0.10 h516909a_0 conda-forge xorg-libsm 1.2.3 hd9c2040_1000 conda-forge xorg-libx11 1.7.0 h36c2ea0_0 conda-forge xorg-libxau 1.0.9 h14c3975_0 conda-forge xorg-libxdmcp 1.1.3 h516909a_0 conda-forge xorg-libxext 1.3.4 h7f98852_1 conda-forge xorg-libxrender 0.9.10 h7f98852_1003 conda-forge xorg-renderproto 0.11.1 h14c3975_1002 conda-forge xorg-xextproto 7.3.0 h14c3975_1002 conda-forge xorg-xproto 7.0.31 h14c3975_1007 conda-forge xxhash 0.8.0 h7f98852_3 conda-forge xz 5.2.5 h516909a_1 conda-forge yaml 0.2.5 h516909a_0 conda-forge zarr 2.6.1 pyhd8ed1ab_0 conda-forge zict 2.0.0 py_0 conda-forge zipp 3.4.1 pyhd8ed1ab_0 conda-forge zlib 1.2.11 h516909a_1010 conda-forge zstd 1.4.9 ha95c52a_0 conda-forge ```

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edit: added the traceback