Add cpython2_only decorator

The test_pretty.test_dictproxy now is properly skipped on PyPy

IPython/lib/tests/test_pretty.py

@@ -12,7 +12,8 b' import types, string, ctypes'
 import nose.tools as nt
 
 from IPython.lib import pretty
-from IPython.testing.decorators import skip_without, py2_only, py3_only
+from IPython.testing.decorators import (skip_without, py2_only, py3_only,
+                                        cpython2_only)
 from IPython.utils.py3compat import PY3, unicode_to_str
 
 if PY3:
@@ -483,7 +484,7 b' def test_mappingproxy():'
     for obj, expected in cases:
         nt.assert_equal(pretty.pretty(obj), expected)
 
-@py2_only
+@cpython2_only # In PyPy, types.DictProxyType is dict
 def test_dictproxy():
     # This is the dictproxy constructor itself from the Python API,
     DP = ctypes.pythonapi.PyDictProxy_New

IPython/testing/decorators.py

@@ -48,7 +48,7 b' from .ipunittest import ipdoctest, ipdocstring'
 from IPython.external.decorators import *
 
 # For onlyif_cmd_exists decorator
-from IPython.utils.py3compat import string_types, which, PY2, PY3
+from IPython.utils.py3compat import string_types, which, PY2, PY3, PYPY
 
 #-----------------------------------------------------------------------------
 # Classes and functions
@@ -336,6 +336,7 b" skip_known_failure = knownfailureif(True,'This test is known to fail')"
 known_failure_py3 = knownfailureif(sys.version_info[0] >= 3, 
                                     'This test is known to fail on Python 3.')
 
+cpython2_only = skipif(PY3 or PYPY, "This test only runs on CPython 2.")
 py2_only = skipif(PY3, "This test only runs on Python 2.")
 py3_only = skipif(PY2, "This test only runs on Python 3.")
 

IPython/utils/py3compat.py

@@ -292,6 +292,7 b' else:'
 
 
 PY2 = not PY3
+PYPY = any(k.startswith("pypy") for k in dir(sys))
 
 
 def annotate(**kwargs):