Log Message:
py-matplotlib: updated to 3.1.0

REL: v3.1.0
The first release of the v3.1 series
This version of Matplotlib support Python 3.6+
Highlights of this release include:
 - A helper method for scatter legends
 - Secondary axis support (ex, degrees and radians)
 - A concise date formatter
 - No longer requires a framework build of Python to use OSX backend
 - Major and minor ticks will no longer collide by default
 - A progress callback for animations
 - mplot3D is always registered
 - deprecated mlab functions have been removed
 - Many function calls have become stricter about invalid or ignored input

REL: v3.0.3
The third and last planned bug-fix release of the 3.0 series
* fix several possible memory leaks
* documentation fixes

jquery-ui is no longer bundled in git repo and is downloaded during
the install or sdist process. If you are installing from pypi the
files will be included, but if you are installing from git you will
need internet access the first time you run `pip install .`. The
install process tries to cache the files and will not need internet
access on future installations.

REL: v3.0.2
This is the second bug-fix release for the v3.0 series.
 - Un-breaks basemap which was broken by partially restoring
   private APIs for cartopy.
 - Fixes bug in warning code when used in an embedded context.
 - Fixes crash when using Tk and closing the first open window before showing it
 - Many documentation improvements.
 - Restore a corner case on ColorBar tick usage.
 - Change the default behavior of `matplotlib.use` to silently allow
   more 'safe' switching after auto-discovery, but before starting an event loop.
 - Improvements to bounding box calculations.
 - Provide the correct length for RcParams instances.

REL: v3.0.1
This is the first bug fix release for the 3.0 series which fixes
several
 - Fix failure to import bug when used with backend-fallback on Python
   3.6.7 and 3.7.1
 - Fixed a number of failure to import bugs around finding fonts
 - Fix Qt4 backend
 - Fix bug on OSX that recursively searched current directory for fonts
 - Fix bouncing-rocket on OSX when doing backend fallback and not
   selecting OSX
 - Temporarily restore several private APIs to unbreak cartopy
 - Make pyplot more tolerant of varying signatures in 3rd-party
   sub-classe
 - Improve datetime64 unit handling
 - Fixed several poor interactions with tight_layout

REL: v3.0.0
The first release of the Matplotlib 3.0 series
This is the first version of Matplotlib to only support Python 3.
Highlights of this release include:
 - GUI backend is selected at run-time based on what toolkits are
   installed.  A GUI toolkit will not be selected on a headless
   server.
 - New cyclic color map *twilight*
 - Improvements to automatic layout of titles, ticks, and GridSpec
 - Many bug fixes!