Address review comments

src/slotscheck/cli.py

@@ -42,6 +42,7 @@
 from .discovery import (
     AbsPath,
     FailedImport,
+    FileNotInSysPathError,
     ModuleLocated,
     ModuleName,
     ModuleTree,
@@ -162,9 +163,9 @@ def root(
 
     try:
         classes, modules = _collect(files, module, conf)
-    except ModuleNotFoundError as e:
+    except (ModuleNotFoundError, FileNotInSysPathError) as e:
         print(
-            f"ERROR: Module '{e.name}' not found.\n\n"
+            f"ERROR: {e}.\n\n"
             "See slotscheck.rtfd.io/en/latest/discovery.html\n"
             "for help resolving common import problems."
         )

src/slotscheck/discovery.py

@@ -165,7 +165,7 @@ def module_tree(
     except BaseException as e:
         return FailedImport(module, e)
     if spec is None:
-        raise ModuleNotFoundError(f"No module named '{module}'", name=module)
+        raise ModuleNotFoundError(f"No module named {module!r}", name=module)
     *namespaces, name = module.split(".")
     location = Path(spec.origin) if spec.has_location and spec.origin else None
     tree: ModuleTree
@@ -292,6 +292,12 @@ class ModuleLocated(NamedTuple):
     expected_location: Optional[AbsPath]
 
 
+class FileNotInSysPathError(Exception):
+    def __init__(self, file: Path) -> None:
+        super().__init__(f"File {str(file)!r} is not in PYTHONPATH")
+        self.file = file
+
+
 def _is_module(p: AbsPath) -> bool:
     return (p.is_file() and p.suffixes == [".py"]) or _is_package(p)
 
@@ -308,7 +314,7 @@ def _module_parents(
         if pp in sys_path:
             return
         yield pp
-    raise ModuleNotFoundError(f"No module named '{p.stem}'", name=p.stem)
+    raise FileNotInSysPathError(p)
 
 
 def _find_modules(

tests/src/test_cli.py

@@ -1,4 +1,5 @@
 import os
+import re
 from importlib.util import find_spec
 from pathlib import Path
 
@@ -33,22 +34,23 @@ def test_module_doesnt_exist(runner: CliRunner):
     assert result.exit_code == 1
     assert isinstance(result.exception, SystemExit)
     assert result.output == (
-        "ERROR: Module 'foo' not found.\n\n"
+        "ERROR: No module named 'foo'.\n\n"
         "See slotscheck.rtfd.io/en/latest/discovery.html\n"
         "for help resolving common import problems.\n"
     )
 
 
-def test_python_file_not_in_sys_path(runner: CliRunner, tmpdir):
-    file = tmpdir / "foo.py"
+def test_python_file_not_in_sys_path(runner: CliRunner, tmp_path: Path):
+    file = tmp_path / "foo.py"
     file.write_text('print("Hello, world!")', encoding="utf-8")
     result = runner.invoke(cli, [str(file)])
     assert result.exit_code == 1
     assert isinstance(result.exception, SystemExit)
-    assert result.output == (
-        "ERROR: Module 'foo' not found.\n\n"
+    assert re.fullmatch(
+        "ERROR: File '.*/foo.py' is not in PYTHONPATH.\n\n"
         "See slotscheck.rtfd.io/en/latest/discovery.html\n"
-        "for help resolving common import problems.\n"
+        "for help resolving common import problems.\n",
+        result.output,
     )
 
 

tests/src/test_discovery.py

@@ -1,10 +1,12 @@
+from pathlib import Path
 from typing import FrozenSet, List, TypeVar
 from unittest import mock
 
 import pytest
 
 from slotscheck.discovery import (
     FailedImport,
+    FileNotInSysPathError,
     Module,
     ModuleLocated,
     ModuleTree,
@@ -418,10 +420,10 @@ def test_given_init_py(self):
             ModuleLocated("files.subdir.some_module.sub", location)
         ]
 
-    def test_given_file_not_in_sys_path(self, tmp_path):
+    def test_given_file_not_in_sys_path(self, tmp_path: Path):
         location = tmp_path / "foo.py"
         location.touch()
-        with pytest.raises(ModuleNotFoundError, match="foo"):
+        with pytest.raises(FileNotInSysPathError, match=r"foo\.py"):
             list(find_modules(location))