Ignore second fractions in `DateTimeField` schema field.
Ignore second fractions in `DateTimeField` schema field.

ssaavedra/couchdb-python,erikdejonge/rabshakeh-couchdb-python-progress-attachments,hdmessaging/couchbase-mapping-python,jur9526/couchdb-python,oliora/couchdb-python,gcarranza/couchdb-python