Fix for CMIP6 AWI-ESM-1-1-LR parent time units

esmvalcore/cmor/_fixes/cmip6/awi_esm_1_1_lr.py

@@ -24,6 +24,6 @@ def fix_metadata(self, cubes):
                 if cube.attributes[parent_units] == bad_value:
                     cube.attributes[parent_units] = 'days since 0001-01-01 ' \
                         + '00:00:00'
-            except AttributeError:
+            except (AttributeError, KeyError):
                 pass
         return cubes