Fix bug introduced in #901 and mentioned later in #929. The default behavior of pcolormesh should be to draw no edges if no edgecolors kwarg is provided.

mdboom · mdboom · commit 577689e75841 · 2012-06-07T08:01:39.000-04:00
diff --git a/lib/matplotlib/axes.py b/lib/matplotlib/axes.py
@@ -7202,6 +7202,7 @@ def pcolormesh(self, *args, **kwargs):
         vmax = kwargs.pop('vmax', None)
         shading = kwargs.pop('shading', 'flat').lower()
         antialiased = kwargs.pop('antialiased', False)
+        kwargs.setdefault('edgecolors', 'None')
 
         X, Y, C = self._pcolorargs('pcolormesh', *args)
         Ny, Nx = X.shape
