Backport 1.96 from trunk (because I want Xenofarm to test 2.2.2):

Add a bunch of sys.stdout.flush() calls that will hopefully improve
the usability of the output of the Xenofarm builds.

Lib/test/regrtest.py

@@ -177,6 +177,7 @@ def main(tests=None, testdir=None, verbose=0, quiet=0, generate=0,
     for test in tests:
         if not quiet:
             print test
+            sys.stdout.flush()
         ok = runtest(test, generate, verbose, quiet, testdir)
         if ok > 0:
             good.append(test)
@@ -315,17 +316,21 @@ def runtest(test, generate, verbose, quiet, testdir = None):
     except (ImportError, test_support.TestSkipped), msg:
         if not quiet:
             print "test", test, "skipped --", msg
+            sys.stdout.flush()
         return -1
     except KeyboardInterrupt:
         raise
     except test_support.TestFailed, msg:
         print "test", test, "failed --", msg
+        sys.stdout.flush()
         return 0
     except:
         type, value = sys.exc_info()[:2]
         print "test", test, "crashed --", str(type) + ":", value
+        sys.stdout.flush()
         if verbose:
             traceback.print_exc(file=sys.stdout)
+            sys.stdout.flush()
         return 0
     else:
         if not cfp:
@@ -355,7 +360,9 @@ def runtest(test, generate, verbose, quiet, testdir = None):
         if output == expected:
             return 1
         print "test", test, "produced unexpected output:"
+        sys.stdout.flush()
         reportdiff(expected, output)
+        sys.stdout.flush()
         return 0
 
 def reportdiff(expected, output):