TST: Move matplotlib.use() to before other matplotlib imports

tests/test_plotting.py

@@ -6,6 +6,7 @@ import tempfile
 import unittest
 
 import matplotlib
+matplotlib.use('Agg', warn=False)
 from matplotlib.pyplot import Artist, savefig, clf
 from matplotlib.testing.noseclasses import ImageComparisonFailure
 from matplotlib.testing.compare import compare_images
@@ -14,7 +15,6 @@ from six.moves import xrange
 
 from geopandas import GeoSeries
 
-matplotlib.use('Agg', warn=False)
 
 # If set to True, generate images rather than perform tests (all tests will pass!)
 GENERATE_BASELINE = False