Add deprecation warning for py35.

Author: a-feld

newrelic/config.py

@@ -16,6 +16,7 @@
 import sys
 import logging
 import traceback
+import warnings
 
 try:
     import ConfigParser
@@ -2755,6 +2756,14 @@ def _setup_agent_console():
 def initialize(config_file=None, environment=None, ignore_errors=None,
             log_file=None, log_level=None):
 
+    version_info = sys.version_info[:2]
+    if version_info == (3, 5):
+        warnings.warn('A future version of the newrelic package will drop '
+                'support for Python 3.5. Please upgrade your version of '
+                'Python.',
+                DeprecationWarning,
+                stacklevel=2)
+
     if config_file is None:
         config_file = os.environ.get('NEW_RELIC_CONFIG_FILE', None)