Add closing quote

Author: m-aciek

Lib/gettext.py

@@ -411,7 +411,7 @@ def _parse(self, fp):
                             self._charset = v.split('charset=')[1]
                         except IndexError:
                             raise ValueError(
-                                f"invalid content-type syntax in '{filename}: '{v}'. Expected 'charset='."
+                                f"invalid content-type syntax in '{filename}': '{v}'. Expected 'charset='."
                             ) from None
                     elif k == 'plural-forms':
                         v = v.split(';')