Don't use FileType for param-file

[jordan-palacios]

As it is, the spawner.py crashes when reading the param_file argument since it is of type FileType instead of string.

See the following traceback:

Traceback (most recent call last):
  File "/home/user/exchange/tiago_ws/install/controller_manager/lib/controller_manager/spawner.py", line 141, in <module>
    sys.exit(main())
  File "/home/user/exchange/tiago_ws/install/controller_manager/lib/controller_manager/spawner.py", line 101, in main
    ret = subprocess.run(['ros2', 'param', 'load', controller_name,
  File "/usr/lib/python3.8/subprocess.py", line 489, in run
    with Popen(*popenargs, **kwargs) as process:
  File "/usr/lib/python3.8/subprocess.py", line 854, in __init__
    self._execute_child(args, executable, preexec_fn, close_fds,
  File "/usr/lib/python3.8/subprocess.py", line 1637, in _execute_child
    self.pid = _posixsubprocess.fork_exec(
TypeError: expected str, bytes or os.PathLike object, not _io.TextIOWrapper

FileType is used for opening the selected file and returns a handle to it. The caller is also responsible for closing the handle later.

This is not the intention of the spawner.py script since we only wish to pass the specified file path to the ros2 param load command.

[Karsten1987]

I actually think that FileType is the right thing to do here as it directly checks whether the file is available or not.
Couldn't we change the line below as such?

param_file = args.param_file.name

[jordan-palacios]

That would work too. But as I said, FileType also give you a file handle you have to manage. And that does not really make sense since we don't want to access the file at all.

The script ends up calling ros2 param load which already checks for file existence (and reports the proper error). If that is not enough we can add a simple os.path.exists(path) here and be done with it.

[Karsten1987]

os.path.exists(path) would make sense to me!

[jordan-palacios]

os.path.exists(path) would make sense to me!

Done!

Failing CI job does not seem to be related to this PR.