Let ffmpeg report errors.

anntzer · anntzer · commit 2b1795351e02 · 2019-01-11T11:10:54.000+01:00
at -loglevel errors, one gets for example the error messages for
non-existent directories ("/foo/bar/baz.mp4: no such file or directory"),
which get then picked up by Matplotlib's logging.
diff --git a/lib/matplotlib/animation.py b/lib/matplotlib/animation.py
@@ -625,7 +625,7 @@ def _args(self):
         # If you have a lot of frames in your animation and set logging to
         # DEBUG, you will have a buffer overrun.
         if _log.getEffectiveLevel() > logging.DEBUG:
-            args += ['-loglevel', 'quiet']
+            args += ['-loglevel', 'error']
         args += ['-i', 'pipe:'] + self.output_args
         return args
 
