fixes logic that loads _module, due to API change in Python 3.9

src/ploomber/env/EnvDict.py

@@ -276,22 +276,29 @@ def raw_preprocess(raw, path_to_raw):
                 raise ValueError('_module cannot be {{here}} if '
                                  'not loaded from a file')
         else:
-            try:
+            # check if it's a filesystem path
+            as_path = Path(module)
+
+            if as_path.exists():
+                if as_path.is_file():
+                    raise ValueError(
+                        'Could not resolve _module "{}", '
+                        'expected a module or a directory but got a '
+                        'file'.format(module))
+                else:
+                    path_to_module = as_path
+
+            # must be a dotted path
+            else:
                 module_spec = importlib.util.find_spec(module)
-            except ValueError:
-                # raises ValueError if passed "."
-                module_spec = None
-
-            if not module_spec:
-                path_to_module = Path(module)
 
-                if not (path_to_module.exists() and path_to_module.is_dir()):
+                # package does not exist
+                if module_spec is None:
                     raise ValueError('Could not resolve _module "{}", '
-                                     'failed to import as a module '
-                                     'and is not a directory'.format(module))
-
-            else:
-                path_to_module = Path(module_spec.origin).parent
+                                     'it is not a valid module '
+                                     'nor a directory'.format(module))
+                else:
+                    path_to_module = Path(module_spec.origin).parent
 
             preprocessed['_module'] = path_to_module
 

tests/env/test_env.py

@@ -143,7 +143,18 @@ def test_init_with_nonexistent_package(cleanup_env):
         Env({'_module': 'i_do_not_exist'})
 
     expected = ('Could not resolve _module "i_do_not_exist", '
-                'failed to import as a module and is not a directory')
+                'it is not a valid module nor a directory')
+    assert exc_info.value.args[0] == expected
+
+
+def test_init_with_file(tmp_directory, cleanup_env):
+    Path('not_a_package').touch()
+
+    with pytest.raises(ValueError) as exc_info:
+        Env({'_module': 'not_a_package'})
+
+    expected = ('Could not resolve _module "not_a_package", '
+                'expected a module or a directory but got a file')
     assert exc_info.value.args[0] == expected