Consistently catch exceptions in index.py

In index.py we were catching requests.exceptions.RetryError and
requests.exceptions.SSLError but then also caught requests.HTTPError.
For consistency catch all of these requests exceptions using the
requests.exceptions path.

Author: cboylan

news/85016e72-3c01-455a-ad4e-e25f676c7381.trivial

@@ -16,7 +16,7 @@
 from pip._vendor.packaging import specifiers
 from pip._vendor.packaging.utils import canonicalize_name
 from pip._vendor.packaging.version import parse as parse_version
-from pip._vendor.requests.exceptions import RetryError, SSLError
+from pip._vendor.requests.exceptions import HTTPError, RetryError, SSLError
 from pip._vendor.six.moves.urllib import parse as urllib_parse
 from pip._vendor.six.moves.urllib import request as urllib_request
 
@@ -237,7 +237,7 @@ def _get_html_page(link, session=None):
             'Skipping page %s because the %s request got Content-Type: %s',
             link, exc.request_desc, exc.content_type,
         )
-    except requests.HTTPError as exc:
+    except HTTPError as exc:
         _handle_get_page_fail(link, exc)
     except RetryError as exc:
         _handle_get_page_fail(link, exc)