Hammer CLI

Cloned from https://bugzilla.redhat.com/show_bug.cgi?id=1244821
Description of problem:

Hammer does not abort or warn the user if the configuration file does not exists. Instead it silently ignores it and switches to interactive mode and asks for the Username and password.

# hammer -c /notexistingfile.conf user list
[Foreman] Username: admin
[Foreman] Password for admin:
---|--------|------------|--------------------------------
ID | LOGIN  | NAME       | EMAIL
---|--------|------------|--------------------------------
3  | admin  | Admin User | root@hag.hilti.com
4  | hoici  | hoici      | root@localhost
5  | viewer | viewer     | viewer@li-lc-1578.hag.hilti.com
---|--------|------------|--------------------------------

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:
1. See command above
2.
3.

Actual results:
Interactive input is asked

Expected results:
Abort with an error that the file cannot be found. Alternative is to report a warning and switch to interactive mode

Additional info: