Optimize "open" method with context manager

Replace the classic open() method with opening context
manager to open file so that the file will be closed
even if an exception occurs.

Change-Id: I0d53b7a38fee6a2ef8ce74496d220adc954afb98
1 file changed
tree: 249dbb5295d56a2f7476fae0eba18ed7b72588a7
  1. neutron/