Fix flake8 errors

2 jobs from instance_views in 1 minute 58 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Lint
passed #1147
flake8

00:59

 
  Test
failed #1148
test

00:58

 
Test test
  File "/builds/RECIRCLE/portal/recircle/interface_openstack/test/test_image.py", line 9, in test_fields
image = Image('id', 'name', 'format')
TypeError: __init__() missing 1 required positional argument: 'size'

----------------------------------------------------------------------
Ran 11 tests in 0.016s

FAILED (errors=1)
ERROR: Job failed: exit code 1