TST: update tests\plotting\test_frame.py for mpl 3.1.0 (#26577)

Author: simonjayhawkins

pandas/plotting/_compat.py

@@ -17,3 +17,4 @@ def inner():
 
 _mpl_ge_2_2_3 = _mpl_version('2.2.3', operator.ge)
 _mpl_ge_3_0_0 = _mpl_version('3.0.0', operator.ge)
+_mpl_ge_3_1_0 = _mpl_version('3.1.0', operator.ge)

pandas/tests/plotting/test_frame.py

@@ -23,6 +23,7 @@
 
 from pandas.io.formats.printing import pprint_thing
 import pandas.plotting as plotting
+from pandas.plotting._compat import _mpl_ge_3_1_0
 
 
 @td.skip_if_no_mpl
@@ -68,7 +69,11 @@ def test_plot(self):
         self._check_axes_shape(axes, axes_num=4, layout=(4, 1))
 
         df = DataFrame({'x': [1, 2], 'y': [3, 4]})
-        with pytest.raises(AttributeError, match='Unknown property blarg'):
+        if _mpl_ge_3_1_0():
+            msg = "'Line2D' object has no property 'blarg'"
+        else:
+            msg = "Unknown property blarg"
+        with pytest.raises(AttributeError, match=msg):
             df.plot.line(blarg=True)
 
         df = DataFrame(np.random.rand(10, 3),