Define httpclient.HTTPError.__repr__

This avoids stack overflow in the default `__repr__`.

Fixes tornadoweb#1624

tornado/httpclient.py

@@ -615,6 +615,12 @@ def __init__(self, code, message=None, response=None):
  def __str__(self):
  return "HTTP %d: %s" % (self.code, self.message)
 
+ # There is a cyclic reference between self and self.response,
+ # which breaks the default __repr__ implementation.
+ # (especially on pypy, which doesn't have the same recursion
+ # detection as cpython).
+ __repr__ = __str__
+
 
 class _RequestProxy(object):
  """Combines an object with a dictionary of defaults.

tornado/test/httpclient_test.py

@@ -655,6 +655,15 @@ def test_copy(self):
  self.assertIsNot(e, e2)
  self.assertEqual(e.code, e2.code)
 
- def test_str(self):
+ def test_plain_error(self):
  e = HTTPError(403)
  self.assertEqual(str(e), "HTTP 403: Forbidden")
+ self.assertEqual(repr(e), "HTTP 403: Forbidden")
+
+ def test_error_with_response(self):
+ resp = HTTPResponse(HTTPRequest('https://example.com/'), 403)
+ with self.assertRaises(HTTPError) as cm:
+ resp.rethrow()
+ e = cm.exception
+ self.assertEqual(str(e), "HTTP 403: Forbidden")
+ self.assertEqual(repr(e), "HTTP 403: Forbidden")