Add ability to set different default username.

During cloud init user might want to change default user from the
distribution to something else. It will not be possible to ssh to such
machine using boxpy ssh command - only using ssh directly with the
correct user name would be possible. In this change there is added
possibility for setting username in boxpy_data section with desired
value to be used in ssh command.

box.py

@@ -349,7 +349,7 @@ class FakeLogger:
 class Config:
     ATTRS = ('cpus', 'config', 'creator', 'disable_nested', 'disk_size',
              'distro', 'forwarding', 'hostname', 'key', 'memory', 'name',
-             'port', 'version')
+             'port', 'version', 'username')
 
     def __init__(self, args, vbox=None):
         self.advanced = None
@@ -365,6 +365,7 @@ class Config:
         self.name = args.name  # this one is not stored anywhere
         self.port = None       # at least is not even tried to be retrieved
         self.version = None
+        self.username = None
         self._conf = {}
 
         # set defaults stored in hard coded yaml
@@ -1181,32 +1182,50 @@ def vmcreate(args, conf=None):
 
     # than, let's try to see if boostraping process has finished
     LOG.info('Waiting for cloud init to finish ', end='')
+    username = DISTROS[conf.distro]["username"]
     cmd = ['ssh', '-o', 'StrictHostKeyChecking=no',
            '-o', 'UserKnownHostsFile=/dev/null',
            '-o', 'ConnectTimeout=2',
            '-i', conf.ssh_key_path[:-4],
-           f'ssh://{DISTROS[conf.distro]["username"]}'
+           f'ssh://{username}@localhost:{vbox.vm_info["port"]}',
-           f'@localhost:{vbox.vm_info["port"]}', 'sudo cloud-init status']
+           'sudo cloud-init status']
     try:
         while True:
-            out = Run(cmd).stdout
+            out = Run(cmd)
-            LOG.debug('Out: %s', out)
+            LOG.debug('Out: %s', out.stdout)
 
-            if (not out) or ('status' in out and 'running' in out):
+            if (not out.stdout) or ('status' in out.stdout and
+                                    'running' in out.stdout):
                 LOG.info('.', end='')
                 sys.stdout.flush()
+                if 'Permission denied (publickey)' in out.stderr:
+                    if conf.username and conf.username != username:
+                        username = conf.username
+                        vbox.setextradata('username', username)
+                        cmd[9] = (f'ssh://{username}'
+                                  f'@localhost:{vbox.vm_info["port"]}')
+                        continue
+                    raise PermissionError(f'There is an issue with accessing '
+                                          f'VM with ssh for user {username}. '
+                                          f'Check output in debug mode.')
                 time.sleep(3)
                 continue
 
             LOG.info(' done')
             break
-        out = out.split(':')[1].strip()
+        out = out.stdout.split(':')[1].strip()
         if out != 'done':
             cmd = cmd[:-1]
             cmd.append('cloud-init status -l')
             LOG.warning('Cloud init finished with "%s" status:\n%s', out,
                         Run(cmd).stdout)
 
+    except PermissionError:
+        LOG.info('\n')
+        iso.cleanup()
+        image.cleanup()
+        vbox.destroy()
+        raise
     except KeyboardInterrupt:
         LOG.warning('\nInterrupted, cleaning up')
         iso.cleanup()
@@ -1220,9 +1239,14 @@ def vmcreate(args, conf=None):
 
     # reread config to update fields
     conf = Config(args, vbox)
+    username = DISTROS[conf.distro]["username"]
     LOG.info('You can access your VM by issuing:')
-    LOG.info(f'ssh -p {conf.port} -i {conf.ssh_key_path[:-4]} '
+    if conf.username and conf.username != username:
-             f'{DISTROS[conf.distro]["username"]}@localhost')
+        LOG.info(f'ssh -p {conf.port} -i {conf.ssh_key_path[:-4]} '
+                 f'{conf.username}@localhost')
+    else:
+        LOG.info(f'ssh -p {conf.port} -i {conf.ssh_key_path[:-4]} '
+                 f'{username}@localhost')
     LOG.info('or simply:')
     LOG.info(f'boxpy ssh {conf.name}')
     return 0
@@ -1388,10 +1412,11 @@ def connect(args):
                   f'file.')
         return 16
 
+    username = conf.username or DISTROS[conf.distro]["username"]
     return Run(['ssh', '-o', 'StrictHostKeyChecking=no',
                 '-o', 'UserKnownHostsFile=/dev/null',
                 '-i', conf.ssh_key_path[:-4],
-                f'ssh://{DISTROS[conf.distro]["username"]}'
+                f'ssh://{username}'
                 f'@localhost:{conf.port}'], False).returncode