Merge pull request #908 from Conengmo/python-2-deprecation

Warn for pending deprecation of Python 2.7

Author: ocefpaf

folium/__init__.py

@@ -2,6 +2,9 @@
 
 from __future__ import (absolute_import, division, print_function)
 
+import sys
+import warnings
+
 from branca.colormap import (ColorMap, LinearColormap, StepColormap)
 from branca.element import (CssLink, Div, Element, Figure, Html, IFrame,
                             JavascriptLink, Link, MacroElement)
@@ -29,6 +32,14 @@
     raise ImportError('branca version 0.3.0 or higher is required. '
                       'Update branca with e.g. `pip install branca --upgrade`.')
 
+if sys.version_info < (3, 0):
+    warnings.warn(
+        ("folium will stop working with Python 2.7 starting Jan. 1, 2019."
+         " Please transition to Python 3 before this time."
+         " Check out https://python3statement.org/ for more info."),
+        PendingDeprecationWarning
+    )
+
 __version__ = get_versions()['version']
 del get_versions