Merged revisions 81967 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk

........
  r81967 | mark.dickinson | 2010-06-13 11:50:29 +0100 (Sun, 13 Jun 2010) | 4 lines

  Issue #8986: erfc was raising OverflowError on Linux for arguments in
  the (approximate) range (-27.3, 30.0), as a result of an escaped errno
  value.
........
diff --git a/Lib/test/test_math.py b/Lib/test/test_math.py
index 6c44435..6c07c88 100644
--- a/Lib/test/test_math.py
+++ b/Lib/test/test_math.py
@@ -1042,6 +1042,15 @@
                         accuracy_failure = acc_check(expected, got,
                                                   rel_err = 5e-15,
                                                   abs_err = 5e-15)
+                    elif fn == 'erfc':
+                        # erfc has less-than-ideal accuracy for large
+                        # arguments (x ~ 25 or so), mainly due to the
+                        # error involved in computing exp(-x*x).
+                        #
+                        # XXX Would be better to weaken this test only
+                        # for large x, instead of for all x.
+                        accuracy_failure = ulps_check(expected, got, 2000)
+
                     else:
                         accuracy_failure = ulps_check(expected, got, 20)
                     if accuracy_failure is None: