Description of problem:

If the user is logged into rhui-manager and the cert get deleted somehow, any further user's commands will return an unknown error with a traceback in logs. 


Version-Release number of selected component (if applicable):
>> rpm -qa '*rhui*'
rh-amazon-rhui-client-rhs30-2.2.124-1.el7.noarch
rhui-installer-base-0.0.24-1.el7ui.noarch
rh-rhui-tools-libs-pre.3.0.16-1.el7ui.noarch
rhui-installer-0.0.24-1.el7ui.noarch
rh-rhui-tools-pre.3.0.16-1.el7ui.noarch
rhui-default-ca-1.0-1.noarch
rh-amazon-rhui-client-2.2.118-1.el7.noarch

RHUI ISO 20151013

How reproducible:
always

Steps to Reproduce:
1. open two terminal windows
2. log into rhui-manager in both terminal windows
3. logout in one of them (i.e. the cert will be deleted)
4. try to list the custom repos or make any other request in the second terminal window, get an error and a traceback

Actual results:

An unexpected error has occurred during the last operation.
More information can be found in /root/.rhui/rhui.log.

2016-02-03 10:36:54,435 - <class 'M2Crypto.SSL.SSLError'>
2016-02-03 10:36:54,435 - Unexpected error caught at the shell level
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/rhui/tools/shell.py", line 88, in safe_listen
    self.listen(clear=first_run)
  File "/usr/lib/python2.7/site-packages/rhui/tools/shell.py", line 122, in listen
    Shell.listen(self)
  File "/usr/lib/python2.7/site-packages/rhui/common/shell.py", line 186, in listen
    item.func(*args, **item.kwargs)
  File "/usr/lib/python2.7/site-packages/rhui/tools/screens/repo.py", line 61, in list
    redhat_repos = self.pulp.redhat_repo_list()
  File "/usr/lib/python2.7/site-packages/rhui/tools/pulp_api.py", line 248, in redhat_repo_list
    response = self.repo_group_api.repo_group(GROUP_RED_HAT)
  File "/usr/lib/python2.7/site-packages/pulp/bindings/repo_groups.py", line 93, in repo_group
    return self.server.GET(path)
  File "/usr/lib/python2.7/site-packages/pulp/bindings/server.py", line 91, in GET
    return self._request('GET', path, queries)
  File "/usr/lib/python2.7/site-packages/pulp/bindings/server.py", line 147, in _request
    response_code, response_body = self.server_wrapper.request(method, url, body)
  File "/usr/lib/python2.7/site-packages/pulp/bindings/server.py", line 306, in request
    ssl_context.load_cert(self.pulp_connection.cert_filename)
  File "/usr/lib64/python2.7/site-packages/M2Crypto/SSL/Context.py", line 76, in load_cert
    m2.ssl_ctx_use_cert(self.ctx, certfile)
SSLError: No such file or directory



Expected results:
A helpful message maybe like: "The user certificate wasn't found. Please logout and login again."