Merge pull request matplotlib#11854 from anntzer/matplotlibrcdevnull

Accept anything that's not a directory for $MATPLOTLIBRC.

Author: QuLogic

doc/users/next_whats_new/2018-08-15-AL.rst

@@ -0,0 +1,11 @@
+:orphan:
+
+The MATPLOTLIBRC environment variable can now point to any "file" path
+``````````````````````````````````````````````````````````````````````
+
+This includes device files; in particular, on Unix systems, one can set
+``MATPLOTLIBRC`` to ``/dev/null`` to ignore the user's matplotlibrc file and
+fall back to Matplotlib's defaults.
+
+As a reminder, if ``MATPLOTLIBRC`` points to a directory, Matplotlib will try
+to load the matplotlibrc file from ``$MATPLOTLIBRC/matplotlibrc``.

lib/matplotlib/__init__.py

@@ -130,7 +130,6 @@
 import pprint
 import re
 import shutil
-import stat
 import subprocess
 import tempfile
 import urllib.request
@@ -708,8 +707,7 @@ def matplotlib_fname():
 
     - `$PWD/matplotlibrc`
 
-    - `$MATPLOTLIBRC` if it is a file (or a named pipe, which can be created
-      e.g. by process substitution)
+    - `$MATPLOTLIBRC` if it is not a directory
 
     - `$MATPLOTLIBRC/matplotlibrc`
 
@@ -744,10 +742,8 @@ def gen_candidates():
         yield os.path.join(get_data_path(), 'matplotlibrc')
 
     for fname in gen_candidates():
-        if os.path.exists(fname):
-            st_mode = os.stat(fname).st_mode
-            if stat.S_ISREG(st_mode) or stat.S_ISFIFO(st_mode):
-                break
+        if os.path.exists(fname) and not os.path.isdir(fname):
+            break
     # Return first candidate that is a file, or last candidate if none is
     # valid (in that case, a warning is raised at startup by `rc_params`).
     return fname