Update 'requests' lib to v2.0.

third_party/requests/exceptions.py

 # -*- coding: utf-8 -*-
 
 """
 requests.exceptions
 ~~~~~~~~~~~~~~~~~~~
 
 This module contains the set of Requests' exceptions.
 
 """
 
 
-class RequestException(RuntimeError):
+class RequestException(IOError):
     """There was an ambiguous exception that occurred while handling your
     request."""
 
 
 class HTTPError(RequestException):
     """An HTTP error occurred."""
 
     def __init__(self, *args, **kwargs):
         """ Initializes HTTPError with optional `response` object. """
         self.response = kwargs.pop('response', None)
@@ skipping 23 matching lines @@
 class MissingSchema(RequestException, ValueError):
     """The URL schema (e.g. http or https) is missing."""
 
 
 class InvalidSchema(RequestException, ValueError):
     """See defaults.py for valid schemas."""
 
 
 class InvalidURL(RequestException, ValueError):
     """ The URL provided was somehow invalid. """
+
+
+class ChunkedEncodingError(RequestException):
+    """The server declared chunked encoding but sent an invalid chunk."""