nargs errors for logging_.print_* functions

[j0yu]

rez 2.27.0

I've been running into exceptions with the print functions in logging that various bits or rez calls.

For example, in commands(), if stop('Hello world') is called, the print_error falls over:

Traceback (most recent call last):
  File "/packages/rez/2.27.0/platform-linux/python-2.7/bin/rez/rez", line 4, in <module>
    run()
  File "/packages/rez/2.27.0/platform-linux/python-2.7/lib/python2.7/site-packages/rez-2.27.0-py2.7.egg/rez/cli/_main.py", line 148, in run
    print_error("%s: %s" % (e.__class__.__name__, str(e)))
  File "/packages/rez/2.27.0/platform-linux/python-2.7/lib/python2.7/site-packages/rez-2.27.0-py2.7.egg/rez/utils/logging_.py", line 22, in print_error
    logger.error(msg % nargs)
TypeError: not enough arguments for format string