reqfile: Update extra-index-url/index-url in session from requirements file

Author: Noah Gorny

src/pip/_internal/network/session.py

@@ -305,6 +305,14 @@ def __init__(self, *args, **kwargs):
         for host in trusted_hosts:
             self.add_trusted_host(host, suppress_logging=True)
 
+    def update_index_urls(self, new_index_urls):
+        # type: (List[str]) -> None
+        """
+        :param new_index_urls: New index urls to update the authentication
+            handler with.
+        """
+        self.auth.index_urls = new_index_urls
+
     def add_trusted_host(self, host, source=None, suppress_logging=False):
         # type: (str, Optional[str], bool) -> None
         """

src/pip/_internal/req/req_file.py

@@ -256,6 +256,10 @@ def handle_option_line(
                 value = relative_to_reqs_file
             find_links.append(value)
 
+        if session:
+            # We need to update the auth urls in session
+            session.update_index_urls(index_urls)
+
         search_scope = SearchScope(
             find_links=find_links,
             index_urls=index_urls,