If DevStack is used to instantiate the magnum plugin, and the
devstack localrc/local.conf has the default values for:
LOG_COLOR (default value = True)
SYSLOG (default value = False)
then upon startup (i.e. running DevStack's stack.sh), the magnum devstack
lib calls the DevStack common setup_colorized_logging function, but
without passing the optional 'project_var' and 'user_var' arguments to
this function. As a result, the setup_colorized_logging
function uses its default values of "user_name" and "project_name"
when it defines the logging_context_format_string (which in turn gets
configured in /etc/magnum/magnum.conf). The problem is that "user_name"
and "project_name" are not defined in the API context used by Magnum,
so that whenever the magnum plugin does a logging call, a KeyError
exception for the non-existant key "user_name" is generated.
The fix is to modify the Magnum context to use "user_name" and
"project_name" attributes to be consistent with the default context
format string set up by DevStack.