paramiko python3: stdout and stderr must be a str not bytes

[merinos]

Paramiko doesn't work with Python3. This PR fixes the bug. Without this patch I have the following error:

In [1]: from proxmoxer import ProxmoxAPI
In [2]: proxmox = ProxmoxAPI('fproxmox_server', user='root', backend='ssh_paramiko')
In [3]: proxmox.cluster.resources.get(type='vm')
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-3-69749f99afc9> in <module>()
----> 1 proxmox.cluster.resources.get(type='vm')

~/.venv/cmdb/lib/python3.5/site-packages/proxmoxer/core.py in get(self, *args, **params)
     82 
     83     def get(self, *args, **params):
---> 84         return self(args)._request("GET", params=params)
     85 
     86     def post(self, *args, **data):

~/.venv/cmdb/lib/python3.5/site-packages/proxmoxer/core.py in _request(self, method, data, params)
     72         else:
     73             logger.info('%s %s', method, url)
---> 74         resp = self._store["session"].request(method, url, data=data or None, params=params)
     75         logger.debug('Status code: %s, output: %s', resp.status_code, resp.content)
     76 

~/.venv/cmdb/lib/python3.5/site-packages/proxmoxer/backends/base_ssh.py in request(self, method, url, data, params, headers)
     44         full_cmd = 'pvesh {0}'.format(' '.join(filter(None, (cmd, url, translated_data))))
     45 
---> 46         stdout, stderr = self._exec(full_cmd)
     47         match = lambda s: re.match('\d\d\d [a-zA-Z]', s)
     48         # sometimes contains extra text like 'trying to acquire lock...OK'

~/.venv/cmdb/lib/python3.5/site-packages/proxmoxer/backends/ssh_paramiko.py in _exec(self, cmd)
     57         session = self.ssh_client.get_transport().open_session()
     58         session.exec_command(cmd)
---> 59         stdout = ''.join(session.makefile('rb', -1))
     60         stderr = ''.join(session.makefile_stderr('rb', -1))
     61         return stdout, stderr

TypeError: sequence item 0: expected str instance, bytes found

This PR also fixes paramiko unit tests. TestParamiko return io.BytesIO instead of a list for stdout and
stderr to look like paramiko.channel.channelfile object.

[coveralls]

Coverage remained the same at 82.034% when pulling bad0131 on merinos:python3 into 51da685 on swayf:develop.

[com6056]

Any updates on getting this merged?

[jplitza]

Can confirm that this PR fixes the problem.

[swayf]

sorry for the delay. =) And thank you for the PR =)