MNT: Remove unnecessary use of keys().

Unless it adds clarity, it's best to just rely on the fact that
iteration on a dictionary (including conversion to list) uses the keys
anyway.

metpy/io/nexrad.py

@@ -265,7 +265,7 @@ def _read_data(self):
         # Check if we have any message segments still in the buffer
         if self._msg_buf:
             log.warning('Remaining buffered messages segments for message type(s): %s',
-                        ' '.join(map(str, self._msg_buf.keys())))
+                        ' '.join(map(str, self._msg_buf)))
 
         del self._msg_buf
 

metpy/plots/ctables.py

@@ -28,7 +28,7 @@ def plot_color_gradients(cmap_category, cmap_list, nrows):
        for ax in axes:
            ax.set_axis_off()
 
-   cmaps = list(ctables.registry.keys())
+   cmaps = list(ctables.registry)
    cmaps = [name for name in cmaps if name[-2:]!='_r']
    nrows = len(cmaps)
    gradient = np.linspace(0, 1, 256)

talks/2015 Unidata Users Workshop.ipynb

@@ -846,7 +846,7 @@
     "\n",
     "# Get the Data\n",
     "data = ncss.get_data(query)\n",
-    "list(data.variables.keys())"
+    "list(data.variables)"
    ]
   },
   {