Python 2 iframe renderer follow-on to #1809 (#1822)

* Revert back to makedirs with exist_ok in codegen since this is already Python 3 only
* Follow the Python 3 makedirs implementation by checking isdir rather than errno

Author: jonmmease

Diff for: packages/python/plotly/codegen/utils.py

@@ -31,11 +31,9 @@ def write_source_py(py_source, filepath, leading_newlines=0):
         # Make dir if needed
         # ------------------
         filedir = opath.dirname(filepath)
-        try:
-            os.makedirs(filedir)
-        except OSError as error:
-            if error.errno != errno.EEXIST:
-                raise
+        # The exist_ok kwarg is only supported with Python 3, but that's ok since
+        # codegen is only supported with Python 3 anyway
+        os.makedirs(filedir, exist_ok=True)
 
         # Write file
         # ----------

Diff for: packages/python/plotly/plotly/io/_base_renderers.py

@@ -4,7 +4,7 @@
 import webbrowser
 import inspect
 import os
-import errno
+from os.path import isdir
 
 import six
 from plotly.io import to_json, to_image, write_image, write_html
@@ -568,7 +568,7 @@ def to_mimebundle(self, fig_dict):
         try:
             os.makedirs(self.html_directory)
         except OSError as error:
-            if error.errno != errno.EEXIST:
+            if not isdir(self.html_directory):
                 raise
 
         write_html(