Improve error messages bytes/unicode conversion functions.

diff --git a/tornado/escape.py b/tornado/escape.py
index 688f7f08787ac4dee00c6a09cec7b24bdbd5be84..0dedad5defc84b8539876ac794e593572dddf74f 100644 (file)
--- a/tornado/escape.py
+++ b/tornado/escape.py
@@ -179,7 +179,8 @@ def utf8(value):
     """
     if isinstance(value, _UTF8_TYPES):
         return value
-    assert isinstance(value, unicode_type)
+    assert isinstance(value, unicode_type), \
+        "Expected bytes, unicode, or None; got %r" % type(value)
     return value.encode("utf-8")
 
 _TO_UNICODE_TYPES = (unicode_type, type(None))
@@ -193,7 +194,8 @@ def to_unicode(value):
     """
     if isinstance(value, _TO_UNICODE_TYPES):
         return value
-    assert isinstance(value, bytes_type)
+    assert isinstance(value, bytes_type), \
+        "Expected bytes, unicode, or None; got %r" % type(value)
     return value.decode("utf-8")
 
 # to_unicode was previously named _unicode not because it was private,
@@ -221,7 +223,8 @@ def to_basestring(value):
     """
     if isinstance(value, _BASESTRING_TYPES):
         return value
-    assert isinstance(value, bytes_type)
+    assert isinstance(value, bytes_type), \
+        "Expected bytes, unicode, or None; got %r" % type(value)
     return value.decode("utf-8")