fix: Add missing imports

Author: C0rn3j

musicbrainzngs/musicbrainz.py

@@ -21,6 +21,8 @@
 from musicbrainzngs import compat
 from urllib.parse import urlencode, urlunparse
 from urllib.request import HTTPDigestAuthHandler, HTTPHandler, HTTPPasswordMgr, Request, build_opener
+from http.client import BadStatusLine, HTTPException
+from urllib.error import HTTPError
 
 _version = "0.7.1"
 _log = logging.getLogger("musicbrainzngs")