Applied patch to ClientForm to fix bug with wrong entities. Also added tests and left patch in repo in case we upgrade ClientForm in the future and need to re-apply it

scrapy/tests/test_clientform.py

@@ -0,0 +1,8 @@
+import unittest
+
+from scrapy.xlib import ClientForm
+
+class ClientFormPatchTests(unittest.TestCase):
+
+    def test_patched_unescape_charref(self):
+        self.assertEqual(ClientForm.unescape_charref('c', 'utf-8'), 'c')

scrapy/xlib/ClientForm.patch

@@ -0,0 +1,15 @@
+diff --git a/scrapy/xlib/ClientForm.py b/scrapy/xlib/ClientForm.py
+--- a/scrapy/xlib/ClientForm.py
++++ b/scrapy/xlib/ClientForm.py
+@@ -242,5 +242,10 @@ def unescape_charref(data, encoding):
+     if name.startswith("x"):
+         name, base= name[1:], 16
+-    uc = unichr(int(name, base))
++    try:
++        uc = unichr(int(name, base))
++    except ValueError:
++        # invalid literal for int()
++        # or integer not in unichr()'s range
++        uc = name
+     if encoding is None:
+         return uc

scrapy/xlib/ClientForm.py

@@ -241,7 +241,12 @@ def unescape_charref(data, encoding):
     name, base = data, 10
     if name.startswith("x"):
         name, base= name[1:], 16
-    uc = unichr(int(name, base))
+    try:
+        uc = unichr(int(name, base))
+    except ValueError:
+        # invalid literal for int()
+        # or integer not in unichr()'s range
+        uc = name
     if encoding is None:
         return uc
     else: