Correctly display error when running setup.py test.

We display an error if someone tries to run setup.py test (saying that
one should run tests.py instead), but that doesn't get displayed if
test.local_freetype is set in setup.cfg -- because the test command
considers that equivalent to passing a (non-existent) local_freetype
option to it, and fails first during argument parsing.

As a solution, display the error in the constructor of the command
instead.

setup.py

@@ -125,9 +125,9 @@
 
 
 class NoopTestCommand(TestCommand):
-    def run(self):
+    def __init__(self, dist):
         print("Matplotlib does not support running tests with "
-              "'python setup.py test'. Please run 'python tests.py'")
+              "'python setup.py test'. Please run 'python tests.py'.")
 
 
 class BuildExtraLibraries(BuildExtCommand):