Update requests to 2.21.0

Also updates:
- certifi-2018.11.29
- chardet-3.0.4
- idna-2.8
- urllib3-1.24.1

libs/requests/certs.py

@@ -2,24 +2,17 @@
 # -*- coding: utf-8 -*-
 
 """
-certs.py
-~~~~~~~~
+requests.certs
+~~~~~~~~~~~~~~
 
-This module returns the preferred default CA certificate bundle.
+This module returns the preferred default CA certificate bundle. There is
+only one — the one from the certifi package.
 
 If you are packaging Requests, e.g., for a Linux distribution or a managed
 environment, you can change the definition of where() to return a separately
 packaged CA bundle.
 """
-import os.path
-
-try:
-    from certifi import where
-except ImportError:
-    def where():
-        """Return the preferred certificate bundle."""
-        # vendored bundle inside Requests
-        return os.path.join(os.path.dirname(__file__), 'cacert.pem')
+from certifi import where
 
 if __name__ == '__main__':
     print(where())