ProjectError class have no msg attribute

[anton44eg]

$ docker-compose up
Traceback (most recent call last):
File "/usr/local/Cellar/docker-compose/1.7.1/libexec/bin/docker-compose", line 9, in <module>
load_entry_point('docker-compose==1.7.1', 'console_scripts', 'docker-compose')()
File "/usr/local/Cellar/docker-compose/1.7.1/libexec/lib/python2.7/site-packages/compose/cli/main.py", line 63, in main
log.error(e.msg)
AttributeError: 'ProjectError' object has no attribute 'msg'

[aanand]

Closed in #3433