TST: skip assert for mpl 3.1+ (#26715)

* TST: skip assert for mpl 3.1+

* MPL compat

* remove pyarrow

* mpl compat

Author: TomAugspurger

ci/deps/travis-36-cov.yaml

@@ -20,7 +20,8 @@ dependencies:
   # https://github.com/pydata/pandas-gbq/issues/271
   - google-cloud-bigquery<=1.11
   - psycopg2
-  - pyarrow=0.9.0
+  # pyarrow segfaults on load: https://github.com/pandas-dev/pandas/issues/26716
+  # - pyarrow=0.9.0
   - pymysql
   - pytables
   - python-snappy

pandas/tests/plotting/common.py

@@ -36,6 +36,7 @@ def setup_method(self, method):
 
         self.mpl_ge_2_2_3 = plotting._compat._mpl_ge_2_2_3()
         self.mpl_ge_3_0_0 = plotting._compat._mpl_ge_3_0_0()
+        self.mpl_ge_3_1_0 = plotting._compat._mpl_ge_3_1_0()
 
         self.bp_n_objects = 7
         self.polycollection_factor = 2
@@ -440,10 +441,18 @@ def _check_grid_settings(self, obj, kinds, kws={}):
         import matplotlib as mpl
 
         def is_grid_on():
-            xoff = all(not g.gridOn
-                       for g in self.plt.gca().xaxis.get_major_ticks())
-            yoff = all(not g.gridOn
-                       for g in self.plt.gca().yaxis.get_major_ticks())
+            xticks = self.plt.gca().xaxis.get_major_ticks()
+            yticks = self.plt.gca().yaxis.get_major_ticks()
+            # for mpl 2.2.2, gridOn and gridline.get_visible disagree.
+            # for new MPL, they are the same.
+
+            if self.mpl_ge_3_0_0:
+                xoff = all(not g.gridline.get_visible() for g in xticks)
+                yoff = all(not g.gridline.get_visible() for g in yticks)
+            else:
+                xoff = all(not g.gridOn for g in xticks)
+                yoff = all(not g.gridOn for g in yticks)
+
             return not (xoff and yoff)
 
         spndx = 1

pandas/tests/plotting/test_frame.py

@@ -383,8 +383,10 @@ def test_subplots(self):
             for ax in axes[:-2]:
                 self._check_visible(ax.xaxis)  # xaxis must be visible for grid
                 self._check_visible(ax.get_xticklabels(), visible=False)
-                self._check_visible(
-                    ax.get_xticklabels(minor=True), visible=False)
+                if not (kind == 'bar' and self.mpl_ge_3_1_0):
+                    # change https://github.com/pandas-dev/pandas/issues/26714
+                    self._check_visible(
+                        ax.get_xticklabels(minor=True), visible=False)
                 self._check_visible(ax.xaxis.get_label(), visible=False)
                 self._check_visible(ax.get_yticklabels())