Fix memory leak with pytest.raises by using weakref

AUTHORS

@@ -99,6 +99,7 @@ mbyt
 Michael Aquilina
 Michael Birtwell
 Michael Droettboom
+Michael Seifert
 Mike Lundy
 Nicolas Delaby
 Oleg Pidsadnyi

CHANGELOG.rst

@@ -12,6 +12,9 @@
 * When loading plugins, import errors which contain non-ascii messages are now properly handled in Python 2 (`#1998`_).
   Thanks `@nicoddemus`_ for the PR.
 
+* Fixed memory leak in the RaisesContext (pytest.raises) (`#1965`_).
+  Thanks `@MSeifert04`_ for the report the PR.
+
 * Fixed false-positives warnings from assertion rewrite hook for modules that were rewritten but
   were later marked explicitly by ``pytest.register_assert_rewrite``
   or implicitly as a plugin (`#2005`_).

_pytest/_code/code.py

@@ -1,6 +1,7 @@
 import sys
 from inspect import CO_VARARGS, CO_VARKEYWORDS
 import re
+from weakref import ref
 
 import py
 builtin_repr = repr
@@ -230,7 +231,7 @@ class TracebackEntry(object):
                 return False
 
         if py.builtin.callable(tbh):
-            return tbh(self._excinfo)
+            return tbh(None if self._excinfo is None else self._excinfo())
         else:
             return tbh
 
@@ -370,7 +371,7 @@ class ExceptionInfo(object):
         #: the exception type name
         self.typename = self.type.__name__
         #: the exception traceback (_pytest._code.Traceback instance)
-        self.traceback = _pytest._code.Traceback(self.tb, excinfo=self)
+        self.traceback = _pytest._code.Traceback(self.tb, excinfo=ref(self))
 
     def __repr__(self):
         return "<ExceptionInfo %s tblen=%d>" % (self.typename, len(self.traceback))