Fix post-merge failure

Author: vkarak

reframe/frontend/reporting/__init__.py

@@ -31,7 +31,8 @@
 from reframe.core.warnings import suppress_deprecations
 from reframe.utility import nodelist_abbrev, nodelist_expand, OrderedSet
 from .storage import StorageBackend
-from .utility import Aggregator, parse_cmp_spec, parse_query_spec
+from .utility import (Aggregator, parse_cmp_spec,
+                      parse_query_spec, parse_time_period)
 
 # The schema data version
 # Major version bumps are expected to break the validation of previous schemas