sphinxext pot_directive: more robust backend switching

[megies]

I've run into a problem with sphinxext plot_directive during a sphinx build, namely that matplotlib.use("Agg") was showing that warning and not being able to switch the backend. I didn't succeed in debugging where matplotlib was imported before it in the stack (it used to work for our documentation beforehand with the same build routine), but the proposed dynamic fallback to plt.switch_backend() worked like a charm for me.

[jenshnielsen]

I think the warning is due to an internal change in Matplotlib, I believe we are seeing similar warnings in the building of the examples in our own docs.

[megies]

Well, then your docs build can only succeed because it had Agg already set in your config files, I guess? For me sphinx popped up one figure for each plot, because my default obviously is not Agg.

[WeatherGod]

That shouldn't happen (the windows popping up). IIRC, everything is
configured so that AGG is forced for doc builds and it ignores the user's
default configurations. What versions of sphinx and matplotlib are you
using?

On Wed, Sep 9, 2015 at 11:39 AM, Tobias Megies notifications@github.com
wrote:

Well, then your docs build can only succeed because it had Agg already
set in your config files, I guess? For me sphinx popped up one figure for
each plot, because my default obviously is not Agg.

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#5039 (comment)
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[megies]

What versions of sphinx and matplotlib are you using?

anaconda                  2.1.0                np19py27_0  
anaconda-client           1.0.1                    py27_0  
basemap                   1.0.7                np19py27_0  
conda                     3.16.0                   py27_0  
conda-build               1.16.0                   py27_0  
conda-env                 2.4.2                    py27_0  
future                    0.14.3                   py27_0  
matplotlib                1.4.3                np19py27_2  
pip                       7.1.2                    py27_0  
python                    2.7.10                        0  
setuptools                18.1                     py27_0  
sphinx                    1.3.1                    py27_0  
sphinx-bootstrap-theme    0.4.5                     <pip>
sphinx-rtd-theme          0.1.7                     <pip>
sphinx_rtd_theme          0.1.7                    py27_0  

Intended to test a few more combinations of versions, but recently conda is just a real mess for me, switching versions of packages.. kind of like throwing dice, drowning in errors of mpl/qt/pyside/libpng build incompatibilities

[tacaswell]

backported as b34682c