block cx_Oracle 6.4
block cx_Oracle 6.4

Prevents https://github.com/oracle/python-cx_Oracle/issues/199

Change-Id: I0f94bde38919a027f094ca016621c1364e845332

j5int/sqlalchemy,zzzeek/sqlalchemy,j5int/sqlalchemy,sqlalchemy/sqlalchemy,monetate/sqlalchemy,monetate/sqlalchemy,graingert/sqlalchemy,wujuguang/sqlalchemy,wujuguang/sqlalchemy,graingert/sqlalchemy