Catch TraversalError, raised by Traversable.joinpath()

Exercising the `Traversable` protocol's concrete methods
has highlighted that `.joinpath()` raises `TraversalError`,
which needs to be caught in several places.

This is primarily resolved within the test suite,
but implicates the `is_resource()` function as well.

Author: kurtmckee

importlib_resources/_functional.py

@@ -3,6 +3,7 @@
 import warnings
 
 from ._common import as_file, files
+from .abc import TraversalError
 
 _MISSING = object()
 
@@ -41,7 +42,10 @@ def is_resource(anchor, *path_names):
 
     Otherwise returns ``False``.
     """
-    return _get_resource(anchor, path_names).is_file()
+    try:
+        return _get_resource(anchor, path_names).is_file()
+    except TraversalError:
+        return False
 
 
 def contents(anchor, *path_names):

importlib_resources/tests/test_functional.py

@@ -72,7 +72,7 @@ def test_read_text(self):
         # fail with PermissionError rather than IsADirectoryError
         with self.assertRaises(OSError):
             resources.read_text(self.anchor01)
-        with self.assertRaises(OSError):
+        with self.assertRaises((OSError, resources.abc.TraversalError)):
             resources.read_text(self.anchor01, 'no-such-file')
         with self.assertRaises(UnicodeDecodeError):
             resources.read_text(self.anchor01, 'utf-16.file')
@@ -120,7 +120,7 @@ def test_open_text(self):
         # fail with PermissionError rather than IsADirectoryError
         with self.assertRaises(OSError):
             resources.open_text(self.anchor01)
-        with self.assertRaises(OSError):
+        with self.assertRaises((OSError, resources.abc.TraversalError)):
             resources.open_text(self.anchor01, 'no-such-file')
         with resources.open_text(self.anchor01, 'utf-16.file') as f:
             with self.assertRaises(UnicodeDecodeError):
@@ -188,7 +188,7 @@ def test_contents(self):
 
         for path_parts in self._gen_resourcetxt_path_parts():
             with (
-                self.assertRaises(OSError),
+                self.assertRaises((OSError, resources.abc.TraversalError)),
                 warnings_helper.check_warnings((
                     ".*contents.*",
                     DeprecationWarning,