strasbourg: add support for drop=True

(support is added to w.c.s. in #17524)

strasbourg/reprise.py

@@ -51,6 +51,12 @@ except IndexError:
 formdef.fields = [
     fields.PageField(id='1', type='page')
 ]
+try:
+    formdef.data_class().wipe(drop=True)
+except TypeError:
+    # drop=True not yet supported
+    pass
+
 formdef.store() # this will clean the db
 
 field_id = 1