Cast paths to strings (they may be Pathlib instances)

Fixes #192 and replaces #193 and #195

Thanks @browniebroke for the original patches.

tests/test_whitenoise.py

@@ -1,11 +1,13 @@
 import os
 import tempfile
+import unittest
 from unittest import TestCase
 try:
     from urllib.parse import urljoin
 except ImportError:
     from urlparse import urljoin
 import shutil
+import sys
 import warnings
 from wsgiref.simple_server import demo_app
 
@@ -255,3 +257,10 @@ def test_immutable_file_test_accepts_regex(self):
         instance = WhiteNoise(None, immutable_file_test=r'\.test$')
         self.assertTrue(instance.immutable_file_test('', '/myfile.test'))
         self.assertFalse(instance.immutable_file_test('', 'file.test.txt'))
+
+    @unittest.skipIf(sys.version_info < (3, 4), "Pathlib was added in Python 3.4")
+    def test_directory_path_can_be_pathlib_instance(self):
+        from pathlib import Path
+        root = Path(Files('root').directory)
+        # Check we can construct instance without it blowing up
+        WhiteNoise(None, root=root, autorefresh=True)

whitenoise/base.py

@@ -88,7 +88,7 @@ def serve(static_file, environ, start_response):
             return []
 
     def add_files(self, root, prefix=None):
-        root = decode_if_byte_string(root)
+        root = decode_if_byte_string(root, force_text=True)
         root = root.rstrip(os.path.sep) + os.path.sep
         prefix = decode_if_byte_string(prefix)
         prefix = ensure_leading_trailing_slash(prefix)

whitenoise/string_utils.py

@@ -3,13 +3,17 @@
 
 if sys.version_info[0] >= 3:
     BINARY_TYPE = bytes
+    TEXT_TYPE = str
 else:
     BINARY_TYPE = str
+    TEXT_TYPE = unicode
 
 
-def decode_if_byte_string(s):
+def decode_if_byte_string(s, force_text=False):
     if isinstance(s, BINARY_TYPE):
         s = s.decode('utf-8')
+    if force_text and not isinstance(s, TEXT_TYPE):
+        s = TEXT_TYPE(s)
     return s