Fix invalid checks for axes_class parameter in ImageGrid.

The validation of the axes_class parameter in the Grid and ImageGrid
class have been wrong ever since they were merged in in f44235e
(relevant followup commits: 7482fdc, a5e67b9).

- In Grid, self._defaultAxesClass has never been a class with its own
  .Axes attribute, so the subclass check would fail with an
  AttributeError.
- In ImageGrid, the `isinstance(axes_class, Axes)` check should be
  `issubclass(...)` instead.  (The code later calls `axes_class(...)`
  to build an axes instance so if one really passed an axes instance,
  the call would raise an exception as axes are not callable.)

Fix these checks.  As a consequence, there was no previously valid
path where axes_class_args would have been set, and passing a
`(class, args)` pair is not documented anyways, so drop that
"functionality" (which never worked).

Author: anntzer

lib/mpl_toolkits/axes_grid1/axes_grid.py

@@ -2,7 +2,6 @@
 
 import matplotlib as mpl
 from matplotlib import cbook
-import matplotlib.axes as maxes
 import matplotlib.ticker as ticker
 from matplotlib.gridspec import SubplotSpec
 
@@ -191,14 +190,6 @@ def __init__(self, fig,
 
         if axes_class is None:
             axes_class = self._defaultAxesClass
-            axes_class_args = {}
-        else:
-            if (isinstance(axes_class, type)
-                    and issubclass(axes_class,
-                                   self._defaultAxesClass.Axes)):
-                axes_class_args = {}
-            else:
-                axes_class, axes_class_args = axes_class
 
         self.axes_all = []
         self.axes_column = [[] for _ in range(self._ncols)]
@@ -246,8 +237,7 @@ def __init__(self, fig,
                 else:
                     sharey = None
 
-            ax = axes_class(fig, rect, sharex=sharex, sharey=sharey,
-                            **axes_class_args)
+            ax = axes_class(fig, rect, sharex=sharex, sharey=sharey)
 
             if share_all:
                 if self._refax is None:
@@ -529,12 +519,6 @@ def __init__(self, fig,
 
         if axes_class is None:
             axes_class = self._defaultAxesClass
-            axes_class_args = {}
-        else:
-            if isinstance(axes_class, maxes.Axes):
-                axes_class_args = {}
-            else:
-                axes_class, axes_class_args = axes_class
 
         self.axes_all = []
         self.axes_column = [[] for _ in range(self._ncols)]
@@ -581,8 +565,7 @@ def __init__(self, fig,
                 sharex = self._column_refax[col]
                 sharey = self._row_refax[row]
 
-            ax = axes_class(fig, rect, sharex=sharex, sharey=sharey,
-                            **axes_class_args)
+            ax = axes_class(fig, rect, sharex=sharex, sharey=sharey)
 
             self.axes_all.append(ax)
             self.axes_column[col].append(ax)