BUG: clearn the figure windows created by tests

fixed: FAILED pandas/tests/plotting/test_datetimelike.py::TestTSPlot::test_ts_plot_with_tz['UTC']

Author: onshek

pandas/tests/plotting/test_converter.py

@@ -70,15 +70,17 @@ def test_registering_no_warning(self):
         # Set to the "warn" state, in case this isn't the first test run
         register_matplotlib_converters()
         ax.plot(s.index, s.values)
+        plt.close()
 
     def test_pandas_plots_register(self):
-        pytest.importorskip("matplotlib.pyplot")
+        plt = pytest.importorskip("matplotlib.pyplot")
         s = Series(range(12), index=date_range("2017", periods=12))
         # Set to the "warn" state, in case this isn't the first test run
         with tm.assert_produces_warning(None) as w:
             s.plot()
 
         assert len(w) == 0
+        plt.close()
 
     def test_matplotlib_formatters(self):
         units = pytest.importorskip("matplotlib.units")
@@ -108,6 +110,7 @@ def test_option_no_warning(self):
         register_matplotlib_converters()
         with ctx:
             ax.plot(s.index, s.values)
+        plt.close()
 
     def test_registry_resets(self):
         units = pytest.importorskip("matplotlib.units")