    def lint(self, fname, cmd=None):
        rel_fname = self.get_rel_fname(fname)
        try:
            code = Path(fname).read_text(encoding=self.encoding, errors="replace")
…
        if callable(cmd):
            lintres = cmd(fname, rel_fname, code)
        elif cmd:
            lintres = self.run_cmd(cmd, rel_fname, code)
        else:
            lintres = basic_lint(rel_fname, code)

        if not lintres:
            return

        res = "# Fix any errors below, if possible.\n\n"
        res += lintres.text
        res += "\n"
        res += tree_context(rel_fname, code, lintres.lines)

        return res

    def py_lint(self, fname, rel_fname, code):
        basic_res = basic_lint(rel_fname, code)
        compile_res = lint_python_compile(fname, code)
        flake_res = self.flake8_lint(rel_fname)
…
    def flake8_lint(self, rel_fname):
        fatal = "E9,F821,F823,F831,F406,F407,F701,F702,F704,F706"
        flake8_cmd = [
            sys.executable,
            "-m",
            "flake8",
            f"--select={fatal}",
            "--show-source",
            "--isolated",
            rel_fname,
        ]
…
def lint_python_compile(fname, code):
    try:
        compile(code, fname, "exec")  # USE TRACEBACK BELOW HERE
        return

Warm-up