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/hooks.py

@@ -10,36 +10,25 @@ Available hooks:
 
 ``response``:
     The response generated from a Request.
-
 """
-
-
 HOOKS = ['response']
 
 
 def default_hooks():
-    hooks = {}
-    for event in HOOKS:
-        hooks[event] = []
-    return hooks
+    return {event: [] for event in HOOKS}
 
 # TODO: response is the only one
 
 
 def dispatch_hook(key, hooks, hook_data, **kwargs):
     """Dispatches a hook dictionary on a given piece of data."""
-
-    hooks = hooks or dict()
-
-    if key in hooks:
-        hooks = hooks.get(key)
-
+    hooks = hooks or {}
+    hooks = hooks.get(key)
+    if hooks:
         if hasattr(hooks, '__call__'):
             hooks = [hooks]
-
         for hook in hooks:
             _hook_data = hook(hook_data, **kwargs)
             if _hook_data is not None:
                 hook_data = _hook_data
-
     return hook_data