issues: 708459047

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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
708459047 MDU6SXNzdWU3MDg0NTkwNDc= 4457 Silently ignoring user passed `engine` key in some cases when opening file objects 226037 closed 0     0 2020-09-24T20:37:37Z 2020-09-28T15:42:01Z 2020-09-28T15:42:01Z MEMBER      

What happened:

When I open() a netCDF4 file and pass the file object to xr.open_dataset with engine='scipy' xarray silently ignores the value of the engine keyword and opens the file with h5netcdf. When opening an netCDF3 file with engine='h5netcdf' the scipy engine is used instead without warning.

What you expected to happen:

Silent autodetection of the engine is fine when passing engine=None, but it is very surprising when passing a value explicitly. I would have expected an exception or at least a warning.

Minimal Complete Verifiable Example:

```python

xr.open_dataset('netCDF4.nc', engine='scipy')

KeyError Traceback (most recent call last) [...] TypeError: Error: netCDF4.nc is not a valid NetCDF 3 file If this is a NetCDF4 file, you may need to install the netcdf4 library, e.g.,

        $ pip install netcdf4

fp = open('netCDF4.nc') xr.open_dataset(fp, engine='scipy') <xarray.Dataset> Dimensions: (line: 41587, pixel: 17751) Coordinates: * line (line) int64 0 1 2 3 4 5 ... 41582 41583 41584 41585 41586 * pixel (pixel) int64 0 1 2 3 4 5 ... 17746 17747 17748 17749 17750 Data variables: phase (line, pixel) float32 ... Attributes: Conventions: CF-1.7 [...] ```

 
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   completed 13221727 issue

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