add logic to set realm from pod global_env_vars if provided instead o…

…f assuming realm attribute is defined for each pod variable (#598)

src/varlist_util.py

@@ -261,6 +261,9 @@ def from_struct(cls, global_settings_d, dims_d, name, parent, **kwargs):
         new_kw = global_settings_d.copy()
         new_kw['coords'] = []
         new_kw['convention'] = parent.pod_settings.get('convention', 'cmip')
+        if parent.pod_settings.get('realm', None) is not None:
+            new_kw['realm'] = parent.pod_settings.get('realm')  # populated if realm defined in pod_env_vars instead
+        #  of an attribute for each POD variable
         if 'dimensions' not in kwargs:
             raise ValueError(f"No dimensions specified for Varlist entry {name}.")
         # validate: check for duplicate coord names