Add pyupgrade to pre-commit configuration (#1783)

To help us switch to f-strings and other 3.6+ changes, add pyupgrade to
our pre-commit configuration to keep the codebase clean.

github/GithubObject.py

@@ -1,5 +1,3 @@
-# -*- coding: utf-8 -*-
-
 ############################ Copyrights and license ############################
 #                                                                              #
 # Copyright 2012 Vincent Jacques <vincent@vincent-jacques.net>                 #
@@ -66,7 +64,7 @@ class _BadAttribute:
         )
 
 
-class GithubObject(object):
+class GithubObject:
     """
     Base class for all classes representing objects returned by the API.
     """
@@ -233,13 +231,10 @@ class GithubObject(object):
             for key, element in value.items()
         ):
             return _ValuedAttribute(
-                dict(
-                    (
-                        key,
-                        klass(self._requester, self._headers, element, completed=False),
-                    )
+                {
+                    key: klass(self._requester, self._headers, element, completed=False)
                     for key, element in value.items()
-                )
+                }
             )
         else:
             return _BadAttribute(value, {str: dict})
@@ -269,8 +264,8 @@ class GithubObject(object):
                 if isinstance(v, bytes):
                     v = v.decode("utf-8")
                 if isinstance(v, str):
-                    v = '"{v}"'.format(v=v)
-                yield u"{k}={v}".format(k=k, v=v)
+                    v = f'"{v}"'
+                yield f"{k}={v}"
 
         return "{class_name}({params})".format(
             class_name=self.__class__.__name__,