doctor: fix error when config is on read only partition

src/promnesia/__main__.py

@@ -4,11 +4,12 @@
 import ast
 import importlib
 import inspect
+import os
 from pathlib import Path
 import shutil
 from subprocess import run, check_call, Popen
 import sys
-from tempfile import TemporaryDirectory
+from tempfile import TemporaryDirectory, gettempdir
 from typing import Callable, Sequence, Iterable, Iterator, Union
 
 
@@ -216,15 +217,23 @@ def config_check(args: argparse.Namespace) -> None:
 def _config_check(cfg: Path) -> Iterable[Exception]:
     logger.info('config: %s', cfg)
 
-    def check(cmd: list[str | Path]) -> Iterable[Exception]:
+    def check(cmd: list[str | Path], **kwargs) -> Iterable[Exception]:
         logger.debug(' '.join(map(str, cmd)))
-        res = run(cmd)
+        res = run(cmd, **kwargs)
         if res.returncode > 0:
             yield Exception()
 
     logger.info('Checking syntax...')
     cmd: list[str | Path] = [sys.executable, '-m', 'compileall', cfg]
-    yield from check(cmd)
+    yield from check(
+        cmd,
+        env={
+            **os.environ,
+            # if config is on read only partition, the command would fail due to generated bytecode
+            # so put it in the temporary directory instead
+            'PYTHONPYCACHEPREFIX': gettempdir()
+        },
+    )
 
     # todo not sure if should be more defensive than check_call here
     logger.info('Checking type safety...')