Description of problem:
With the latest version of spacecmd, if I run a command from bash, I run into the following issue:

# spacecmd -d -- user_list
DEBUG: : False
DEBUG: Read configuration from /root/.spacecmd/config
DEBUG: Loading configuration section [spacecmd]
DEBUG: Current Configuration: {'username': 'admin', 'nossl': False, 'server': 'localhost'}
DEBUG: Configuration section [localhost] does not exist
DEBUG: Connecting to https://localhost/rpc/api
DEBUG: Server API Version = 13.0
DEBUG: Using cached credentials from /root/.spacecmd/localhost/session
DEBUG: Loading cache from /root/.spacecmd/localhost/ssm
DEBUG: : False
DEBUG: Loading cache from /root/.spacecmd/localhost/systems
DEBUG: Loading cache from /root/.spacecmd/localhost/errata
DEBUG: Loading cache from /root/.spacecmd/localhost/packages_short
DEBUG: Loading cache from /root/.spacecmd/localhost/packages_long
DEBUG: Loading cache from /root/.spacecmd/localhost/packages_by_id
INFO: Connected to https://localhost/rpc/api as admin
ERROR: SpacewalkShell instance has no attribute 'print_result'
Traceback (most recent call last):
  File "/usr/bin/spacecmd", line 139, in <module>
    shell.print_result(shell.onecmd( precmd ), precmd)
AttributeError: SpacewalkShell instance has no attribute 'print_result'

With an older Version of spacecmd(2.2.5-1.el6.noarch), it is running without any problem.

Version-Release number of selected component (if applicable):
spacecmd-2.2.9-1.el6.noarch

How reproducible:
Install spacecmd in the above version on a satellite5.6 server. I know it is just supported in spacewalk and I will also be able to test it on a spacewalk server in the next days. 

Steps to Reproduce:
1. run satellite5.6
2. run spacecmd in the above version
3. from the bash command line exec any command

Actual results:
ERROR: SpacewalkShell instance has no attribute 'print_result'

Expected results:
I will get an result output of the query

Additional info: