fix the annoying interaction between "pdb.set_trace()" and --pdb. The problem

is that pdb raises BdbQuit on exit, which is then caught by --pdb, showing an
unwanted pdb prompt.  Fix it by making --pdb to ignore BdbQuit

--HG--
branch : trunk

py/_plugin/pytest_pdb.py

@@ -2,7 +2,7 @@
 interactive debugging with the Python Debugger.
 """
 import py
-import pdb, sys, linecache
+import bdb, pdb, sys, linecache
 
 def pytest_addoption(parser):
     group = parser.getgroup("general")
@@ -20,7 +20,8 @@ class PdbInvoke:
         session.config.option.tbstyle = "no"
     def pytest_runtest_makereport(self, item, call, __multicall__):
         if not call.excinfo or \
-            call.excinfo.errisinstance(py.test.skip.Exception):
+            call.excinfo.errisinstance(py.test.skip.Exception) or \
+            call.excinfo.errisinstance(bdb.BdbQuit):
             return
         rep = __multicall__.execute()
         if "xfail" in rep.keywords:

testing/plugin/test_pytest_pdb.py

@@ -39,6 +39,15 @@ class TestPDB:
         assert rep.skipped
         assert len(pdblist) == 0
 
+    def test_pdb_on_BdbQuit(self, testdir, pdblist):
+        rep = testdir.inline_runsource1('--pdb', """
+            import py, bdb
+            def test_func():
+                raise bdb.BdbQuit
+        """)
+        assert rep.failed
+        assert len(pdblist) == 0
+
     def test_pdb_interaction(self, testdir):
         p1 = testdir.makepyfile("""
             def test_1():