Fix CI (MacOS)

Author: jdavid

pygit2/config.py

@@ -176,10 +176,10 @@ def get_multivar(self, name, regex=None):
         to filter the variables we're interested in.
         """
         name = str_to_bytes(name, "name")
+        regex = to_bytes(regex or None)
 
         citer = ffi.new('git_config_iterator **')
-        err = C.git_config_multivar_iterator_new(citer, self._config, name,
-                                                 to_bytes(regex))
+        err = C.git_config_multivar_iterator_new(citer, self._config, name, regex)
         check_error(err)
 
         return ConfigMultivarIterator(self, citer[0])

pygit2/errors.py

@@ -43,7 +43,7 @@ def check_error(err, io=False):
     if giterr != ffi.NULL:
         message = ffi.string(giterr.message).decode('utf8')
     else:
-        message = "err %d (no message provided)" % err
+        message = f"err {err} (no message provided)"
 
     # Translate to Python errors
     if err in value_errors: