id,node_id,number,title,user,state,locked,assignee,milestone,comments,created_at,updated_at,closed_at,author_association,active_lock_reason,draft,pull_request,body,reactions,performed_via_github_app,state_reason,repo,type
972720354,MDExOlB1bGxSZXF1ZXN0NzE0Mjc0ODcw,5710,Fix errors in test_latex_name_isnt_split for min environments,14371165,closed,0,,,7,2021-08-17T13:57:44Z,2021-08-18T03:02:25Z,2021-08-18T02:34:05Z,MEMBER,,0,pydata/xarray/pulls/5710,"There's some error in the minimum environments (for example `ubuntu-latest py37-bare-minimum`) introduced in #5682 but was hidden in all other errors because of #5654:
```
 =========================== short test summary info ============================
ERROR xarray/tests/test_plot.py::test_latex_name_isnt_split - NameError: name...
= 7908 passed, 4163 skipped, 202 xfailed, 42 xpassed, 89 warnings, 1 error in 279.31s (0:04:39) =
```

But when looking further in the details it mentions a completely different function crashing because matplotlib isn't installed, which is true but the function doesn't test any mpl-specific things. 
```
 ==================================== ERRORS ====================================
_______________ ERROR at teardown of test_latex_name_isnt_split ________________
[gw0] linux -- Python 3.7.10 /usr/share/miniconda/envs/xarray-tests/bin/python

    @pytest.fixture(scope=""function"", autouse=True)
    def test_all_figures_closed():
        """"""meta-test to ensure all figures are closed at the end of a test
    
        Notes:  Scope is kept to module (only invoke this function once per test
        module) else tests cannot be run in parallel (locally). Disadvantage: only
        catches one open figure per run. May still give a false positive if tests
        are run in parallel.
        """"""
        yield None
    
>       open_figs = len(plt.get_fignums())
E       NameError: name 'plt' is not defined

/home/runner/work/xarray/xarray/xarray/tests/test_plot.py:72: NameError
```
Might be something that pytest runs on every function. Not sure if there's a clean way of turning it off, but requiring matplotlib to be installed works of course.

<!-- Feel free to remove check-list items aren't relevant to your change -->

- [x] Passes `pre-commit run --all-files`
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