Check for name attribute in source parameter.

Before trying to use it, return None if it's not there.

Fixes #6106

pipenv/project.py

@@ -236,6 +236,8 @@ def get_package_categories(self, for_lockfile=False):
             return ["packages", "dev-packages"] + list(package_categories)
 
     def get_requests_session_for_source(self, source):
+        if not (source and source.get("name")):
+            return None
         if self.sessions.get(source["name"]):
             session = self.sessions[source["name"]]
         else:
@@ -268,6 +270,8 @@ def get_hash_from_link(self, hash_cache, link):
     def get_hashes_from_pypi(self, ireq, source):
         pkg_url = f"https://pypi.org/pypi/{ireq.name}/json"
         session = self.get_requests_session_for_source(source)
+        if not session:
+            return None
         try:
             collected_hashes = set()
             # Grab the hashes from the new warehouse API.