Ensure that we don't overlook errors in first PyObject_RichCompareBool call.

Python 3.5 turns such cases into SystemErrors.

See: https://bugs.python.org/issue23571

Fixes #15.

.travis.yml

@@ -6,6 +6,7 @@ python:
     - 3.2
     - 3.3
     - 3.4
+    - 3.5
     - pypy
     - pypy3
 install:

BTrees/_compat.h

@@ -27,11 +27,15 @@
 #define TEXT_FROM_STRING PyUnicode_FromString
 #define TEXT_FORMAT PyUnicode_Format
 
+/* Note that the second comparison is skipped if the first comparison returns:
+
+   1  -> There was no error and the answer is -1
+  -1 -> There was an error, which the caller will detect with PyError_Occurred.
+ */
 #define COMPARE(lhs, rhs) \
-    PyObject_RichCompareBool((lhs), (rhs), Py_LT) > 0 ? -1 : \
+  PyObject_RichCompareBool((lhs), (rhs), Py_LT) != 0 ? -1 : \
     (PyObject_RichCompareBool((lhs), (rhs), Py_EQ) > 0 ? 0 : 1)
 
-
 #else
 
 #define INTERN PyString_InternFromString

CHANGES.rst

 ``BTrees`` Changelog
 ====================
 
-4.1.5 (unreleased)
+4.2.0 (unreleased)
 ------------------
 
-- TBD
+- Python 3.5 support.
 
 4.1.4 (2015-06-02)
 ------------------

setup.py

@@ -128,6 +128,7 @@ setup(name='BTrees',
         'Programming Language :: Python :: 3.2',
         'Programming Language :: Python :: 3.3',
         'Programming Language :: Python :: 3.4',
+        'Programming Language :: Python :: 3.5',
         "Programming Language :: Python :: Implementation :: CPython",
         "Programming Language :: Python :: Implementation :: PyPy",
         "Framework :: ZODB",