Sync GithubIntegration __init__ arguments with github.Github (#2556)

Github and GithubIntegration now both support the same (full) set of Requester arguments.
Creating a Github instance for a Github App Installation coming from GithubIntegration uses the same
Requester arguments (except for auth).

github/MainClass.py

@@ -83,6 +83,7 @@ class Github:
     This is the main class you instantiate to access the Github API v3. Optional parameters allow different authentication methods.
     """
 
+    # keep non-deprecated arguments in-sync with Requester
     # v2: remove login_or_token, password, jwt and app_auth
     # v2: move auth to the front of arguments
     # v2: add * before first argument so all arguments must be named,
@@ -95,7 +96,7 @@ class Github:
         app_auth=None,
         base_url=Consts.DEFAULT_BASE_URL,
         timeout=Consts.DEFAULT_TIMEOUT,
-        user_agent="PyGithub/Python",
+        user_agent=Consts.DEFAULT_USER_AGENT,
         per_page=Consts.DEFAULT_PER_PAGE,
         verify=True,
         retry=None,
@@ -123,6 +124,8 @@ class Github:
         assert isinstance(base_url, str), base_url
         assert isinstance(timeout, int), timeout
         assert user_agent is None or isinstance(user_agent, str), user_agent
+        assert isinstance(per_page, int), per_page
+        assert isinstance(verify, (bool, str)), verify
         assert (
             retry is None
             or isinstance(retry, int)