Fixes an issue introduced by #832. If multiple users on the same machine have non-writable home directories, the /tmp/matplotlib directory created may be shared. This includes the user's login name in the directory name to prevent that.
Discovered by Matt Anderson.
Put user's name in the temp directory that gets created when the home…
… directory is not writable. Fixes race conditions on a multi-user machine discovered by Matt Anderson.
I see no harm in this change. +1