bimtester: se gettext for message translation

src/ifcbimtester/bimtester/features/steps/ifcdata_methods.py

@@ -0,0 +1,9 @@
+from utils import IfcFile
+
+
+def assert_schema(context, target_schema):
+    real_schema = IfcFile.get().schema
+    assert real_schema == target_schema, (
+        _("We expected a schema of {} but instead got {}")
+        .format(target_schema, real_schema)
+    )