MNT: explicitly cast np.bool_ -> bool to prevent deprecation warning

This is a workaround to https://bugs.python.org/issue37980

- np.bool raises a warning if you try to use it as an index (by
  warning in its `__index__` method
- in py38 python/cpython#11952 python changes
  the code path used to convert `np.bool_` -> int for as it is used in
  `sorted` so it now goes through the `__index__` code path
- this causes a bunch of spurious warnings to come out of Matplotlib.

Author: tacaswell

lib/matplotlib/axes/_base.py

@@ -3213,7 +3213,8 @@ def set_xlim(self, left=None, right=None, emit=True, auto=False,
         reverse = left > right
         left, right = self.xaxis.get_major_locator().nonsingular(left, right)
         left, right = self.xaxis.limit_range_for_scale(left, right)
-        left, right = sorted([left, right], reverse=reverse)
+        # cast to bool to avoid bad interaction between python 3.8 and np.bool_
+        left, right = sorted([left, right], reverse=bool(reverse))
 
         self._viewLim.intervalx = (left, right)
         if auto is not None:
@@ -3597,7 +3598,8 @@ def set_ylim(self, bottom=None, top=None, emit=True, auto=False,
         reverse = bottom > top
         bottom, top = self.yaxis.get_major_locator().nonsingular(bottom, top)
         bottom, top = self.yaxis.limit_range_for_scale(bottom, top)
-        bottom, top = sorted([bottom, top], reverse=reverse)
+        # cast to bool to avoid bad interaction between python 3.8 and np.bool_
+        bottom, top = sorted([bottom, top], reverse=bool(reverse))
 
         self._viewLim.intervaly = (bottom, top)
         if auto is not None:

lib/matplotlib/axis.py

@@ -2169,7 +2169,8 @@ def get_minpos(self):
     def set_inverted(self, inverted):
         # docstring inherited
         a, b = self.get_view_interval()
-        self.axes.set_xlim(sorted((a, b), reverse=inverted), auto=None)
+        # cast to bool to avoid bad interaction between python 3.8 and np.bool_
+        self.axes.set_xlim(sorted((a, b), reverse=bool(inverted)), auto=None)
 
     def set_default_intervals(self):
         # docstring inherited
@@ -2468,7 +2469,8 @@ def get_minpos(self):
     def set_inverted(self, inverted):
         # docstring inherited
         a, b = self.get_view_interval()
-        self.axes.set_ylim(sorted((a, b), reverse=inverted), auto=None)
+        # cast to bool to avoid bad interaction between python 3.8 and np.bool_
+        self.axes.set_ylim(sorted((a, b), reverse=bool(inverted)), auto=None)
 
     def set_default_intervals(self):
         # docstring inherited

lib/mpl_toolkits/mplot3d/axes3d.py

@@ -619,7 +619,8 @@ def set_xlim3d(self, left=None, right=None, emit=True, auto=False,
         reverse = left > right
         left, right = self.xaxis.get_major_locator().nonsingular(left, right)
         left, right = self.xaxis.limit_range_for_scale(left, right)
-        left, right = sorted([left, right], reverse=reverse)
+        # cast to bool to avoid bad interaction between python 3.8 and np.bool_
+        left, right = sorted([left, right], reverse=bool(reverse))
         self.xy_viewLim.intervalx = (left, right)
 
         if auto is not None: