Update warning message to specify HTTP request

src/pip/_internal/index/collector.py

@@ -453,7 +453,7 @@ def _get_html_page(link, session=None):
     except _NotHTTP:
         logger.warning(
             'Skipping page %s because it looks like an archive, and cannot '
-            'be checked by HEAD.', link,
+            'be checked by a HTTP HEAD request.', link,
         )
     except _NotHTML as exc:
         logger.warning(

tests/unit/test_collector.py

@@ -94,7 +94,7 @@ def test_get_html_page_invalid_content_type_archive(caplog, url):
     assert ('pip._internal.index.collector',
             logging.WARNING,
             'Skipping page {} because it looks like an archive, and cannot '
-            'be checked by HEAD.'.format(
+            'be checked by a HTTP HEAD request.'.format(
                 url)) \
         in caplog.record_tuples