Handle authentication for api domains of GitHub/Bitbucket, fixes #9173

src/Composer/Util/AuthHelper.php

@@ -235,6 +235,8 @@ class AuthHelper
                 $this->io->writeError($authenticationDisplayMessage, true, IOInterface::DEBUG);
                 $this->displayedOriginAuthentications[] = $origin;
             }
+        } elseif (in_array($origin, array('api.bitbucket.org', 'api.github.com'), true)) {
+            return $this->addAuthenticationHeader($headers, str_replace('api.', '', $origin), $url);
         }
 
         return $headers;