Merge pull request #6747 from janschulz/better_subprocess_errors

tacaswell · web-flow · commit 4bfeef646bcf · 2016-07-15T21:10:03.000-05:00
Also output the actual error on svg backend tests using subprocess
diff --git a/lib/matplotlib/tests/test_backend_svg.py b/lib/matplotlib/tests/test_backend_svg.py
@@ -153,16 +153,25 @@ def _test_determinism_save(filename, usetex):
 def _test_determinism(filename, usetex):
     import os
     import sys
-    from subprocess import check_call
+    from subprocess import check_output, STDOUT, CalledProcessError
     from nose.tools import assert_equal
     plots = []
     for i in range(3):
-        check_call([sys.executable, '-R', '-c',
-                    'import matplotlib; '
-                    'matplotlib.use("svg"); '
-                    'from matplotlib.tests.test_backend_svg '
-                    'import _test_determinism_save;'
-                    '_test_determinism_save(%r, %r)' % (filename, usetex)])
+        # Using check_output and setting stderr to STDOUT will capture the real
+        # problem in the output property of the exception
+        try:
+            check_output([sys.executable, '-R', '-c',
+                        'import matplotlib; '
+                        'matplotlib.use("svg"); '
+                        'from matplotlib.tests.test_backend_svg '
+                        'import _test_determinism_save;'
+                        '_test_determinism_save(%r, %r)' % (filename, usetex)],
+                        stderr=STDOUT)
+        except CalledProcessError as e:
+            # it's easier to use utf8 and ask for forgiveness than try to figure
+            # out what the current console has as an encoding :-/
+            print(e.output.decode(encoding="utf-8", errors="ignore"))
+            raise e
         with open(filename, 'rb') as fd:
             plots.append(fd.read())
         os.unlink(filename)
