Flycheck Trouble with Tramp and Python: “no module named /ssh:…/home/ubuntu/test.py”

Question

Hi and thank You for helping!

Overview

I run a Linux Container (Guest) on my Machine (Host). On this guest I installed python3. Too, there I have a file "test.py". I edit this file via Emacs Tramp, however the flycheck syntax checker is not working. I suspect this is due to a misconfigured variable "default-directory" on the guest.

Details

System

• Host: Ubuntu 18.04.4 LTS, GNU EMacs 28.0.50; Flycheck version: 32snapshot (package: 20200610.1809)
• Guest/Container: Ubuntu 20.04.1 LTS;

On the guest

File test.py:

print("hello world")

Terminal:

which pylint
#> /usr/local/bin/pylint

pylint test.py
#> test.py:1:0: C0114: Missing module docstring (missing-module-docstring)
#> ------------------------------------------------------------------
#> Your code has been rated at 5.00/10 (previous run: 5.00/10, +0.00)

So far, so good.

Host

On my host I open GNU EMacs and then tramp to /ssh:ubuntu@guest:/home/ubuntu/test.py" on the guest. I am now in test.py remotely. Hitting M-x flycheck-mode.

First line shows this syntax error:

No module named /ssh:ubuntu@phd:/home/ubuntu/PHD/test.py [fatal]

No other syntax errors (of course). I further tried M-x flycheck-compile with python-pylint:

-*- mode: compilation; default-directory: #("/ssh:ubuntu@phd:/home/ubuntu/" 1 4 (helm-ff-file t) 5 11 (helm-ff-file t) 12 15 (helm-ff-file t)) -*-
Compilation started at Mon Aug  3 13:07:20

/usr/bin/python3 -c import\ sys\;sys.path.pop\(0\)\;import\ runpy\;runpy.run_module\(\"pylint\"\) --reports\=n --output-format\=json /ssh\:ubuntu\@phd\:/home/ubuntu/test.py
[
    {
        "type": "fatal",
        "module": "/ssh:ubuntu@guest:/home/ubuntu/test.py",
        "obj": "",
        "line": 1,
        "column": 0,
        "path": "/ssh:ubuntu@guest:test.py",
        "symbol": "fatal",
        "message": "No module named /ssh:ubuntu@guest:test.py",
        "message-id": "F0001"
    }
]

Compilation exited abnormally with code 1 at Mon Aug  3 13:07:21

Same with python-pycompile:

-*- mode: compilation; default-directory: #("/ssh:ubuntu@guest:/home/ubuntu/" 1 4 (helm-ff-file t) 5 11 (helm-ff-file t) 12 15 (helm-ff-file t)) -*-
Compilation started at Mon Aug  3 13:21:58

/usr/bin/python3 -m py_compile /ssh\:ubuntu\@guest\:/home/ubuntu/test.py
Traceback (most recent call last):
  File "/usr/lib/python3.8/runpy.py", line 193, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/usr/lib/python3.8/runpy.py", line 86, in _run_code
    exec(code, run_globals)
  File "/usr/lib/python3.8/py_compile.py", line 218, in <module>
    sys.exit(main())
  File "/usr/lib/python3.8/py_compile.py", line 209, in main
    compile(filename, doraise=True)
  File "/usr/lib/python3.8/py_compile.py", line 142, in compile
    source_bytes = loader.get_data(file)
  File "<frozen importlib._bootstrap_external>", line 972, in get_data
FileNotFoundError: [Errno 2] No such file or directory: '/ssh:ubuntu@phd:/home/ubuntu/test.py'

Compilation exited abnormally with code 1 at Mon Aug  3 13:21:58

The output of flycheck-verify-setup:

Syntax checkers for buffer test.py in python-mode:

First checker to run:

  python-pylint
    - may enable:         yes
    - executable:         Found at /usr/bin/python3
    - configuration file: Not found
    - `pylint' module:    Found at "/usr/local/lib/python3.6/dist-packages/pylint/__init__.py"
    - next checkers:      python-mypy

Checkers that could run if selected:

  python-pycompile  select
    - may enable:    yes
    - executable:    Found at /usr/bin/python3
    - next checkers: python-mypy

Checkers that are compatible with this mode, but will not run until properly configured:

  python-flake8 (automatically disabled) reset
    - may enable:         no
    - executable:         Found at /usr/bin/python3
    - configuration file: Not found
    - `flake8' module:    Missing; sys.path is ['/usr/lib/python36.zip', '/usr/lib/python3.6', '/usr/lib/python3.6/lib-dynload', '/usr/local/lib/python3.6/dist-packages', '/usr/lib/python3/dist-packages']
    - next checkers:      python-pylint, python-mypy

  python-mypy (automatically disabled) reset
    - may enable:         no
    - may run:            t
    - executable:         Not found
    - configuration file: Not found

Flycheck Mode is enabled.  Use C-u C-c ! x to enable disabled checkers.

--------------------

Flycheck version: 32snapshot (package: 20200610.1809)
Emacs version:    28.0.50
System:           x86_64-pc-linux-gnu
Window system:    x

Hypothesis

I think just the default-dir variable pointing to test.py is a misfit in this case. Maybe this is easy to fix and I just missed a point in the manual?

Help highly appreciated.

--

Flychecker is a terrific tool and I cannot imagine not using it - thank You!