Merge pull request matplotlib#22421 from anntzer/fkwo

Make most params to figure()/Figure() kwonly.

Author: timhoffm

doc/api/next_api_changes/deprecations/22421-AL.rst

@@ -0,0 +1,5 @@
+Parameters to ``plt.figure()`` and the ``Figure`` constructor
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+All parameters to `.pyplot.figure` and the `.Figure` constructor, other than
+*num*, *figsize*, and *dpi*, will become keyword-only after a deprecation
+period.

lib/matplotlib/figure.py

@@ -2129,6 +2129,7 @@ def __repr__(self):
             naxes=len(self.axes),
         )
 
+    @_api.make_keyword_only("3.6", "facecolor")
     def __init__(self,
                  figsize=None,
                  dpi=None,

lib/matplotlib/pyplot.py

@@ -667,6 +667,7 @@ def __exit__(self, *args):
 
 ## Figures ##
 
+@_api.make_keyword_only("3.6", "facecolor")
 def figure(num=None,  # autoincrement if None, else integer from 1-N
            figsize=None,  # defaults to rc figure.figsize
            dpi=None,  # defaults to rc figure.dpi