Remove manipulations of mappings while it is being iterated

This behavior will raise starting from python 3.8.

aiida/orm/querybuilder.py

@@ -981,14 +981,17 @@ def _process_filters(self, filters):
         if not isinstance(filters, dict):
             raise InputValidationError('Filters have to be passed as dictionaries')
 
+        processed_filters = {}
+
         for key, value in filters.items():
             if isinstance(value, entities.Entity):
                 # Convert to be the id of the joined entity because we can't query
                 # for the object instance directly
-                filters.pop(key)
-                filters['{}_id'.format(key)] = value.id
+                processed_filters['{}_id'.format(key)] = value.id
+            else:
+                processed_filters[key] = value
 
-        return filters
+        return processed_filters
 
     def _add_type_filter(self, tagspec, classifiers, subclassing):
         """

aiida/tools/importexport/migration/v03_to_v04.py

@@ -24,7 +24,7 @@
 Where id is a SQLA id and migration-name is the name of the particular migration.
 """
 # pylint: disable=invalid-name
-
+import copy
 import os
 
 import numpy as np
@@ -312,7 +312,8 @@ def _migration_calc_job_option_attribute_keys(attr_id, content):
                 'jobresource_params': 'resources',
                 'parser': 'parser_name'
             }
-            for key in content:
+            # Need to loop over a clone because the `content` needs to be modified in place
+            for key in copy.deepcopy(content):
                 if key in key_mapper:
                     content[key_mapper[key]] = content.pop(key)