FIX: over-ride 'copy' on RcParams

tacaswell · tacaswell · commit ae005f3d0165 · 2018-10-23T17:20:45.000-04:00
This is due to a fix on upstream cpython ( python/cpython@d45a961 ) which fixed the copy behavior to fall back to the sub-class's `__getitem__` which seems correct, but we were relying on it _not_ correctly hitting our custom `__getitem__`. closes #12601
diff --git a/lib/matplotlib/__init__.py b/lib/matplotlib/__init__.py
@@ -924,6 +924,10 @@ def find_all(self, pattern):
                         for key, value in self.items()
                         if pattern_re.search(key))
 
+    def copy(self):
+        return {k: dict.__getitem__(self, k)
+                for k in self}
+
 
 def rc_params(fail_on_error=False):
     """Return a :class:`matplotlib.RcParams` instance from the
