allow pdbcls without implying usepdb

_pytest/debugging.py

@@ -20,15 +20,15 @@ def pytest_namespace():
     return {'set_trace': pytestPDB().set_trace}
 
 def pytest_configure(config):
-    if config.getvalue("usepdb") or config.getvalue("usepdb_cls"):
+    if config.getvalue("usepdb_cls"):
+        modname, classname = config.getvalue("usepdb_cls").split(":")
+        __import__(modname)
+        pdb_cls = getattr(sys.modules[modname], classname)
+    else:
+        pdb_cls = pdb.Pdb
+
+    if config.getvalue("usepdb"):
         config.pluginmanager.register(PdbInvoke(), 'pdbinvoke')
-        if config.getvalue("usepdb_cls"):
-            modname, classname = config.getvalue("usepdb_cls").split(":")
-            __import__(modname)
-            pdb_cls = getattr(sys.modules[modname], classname)
-        else:
-            pdb_cls = pdb.Pdb
-        pytestPDB._pdb_cls = pdb_cls
 
     old = (pdb.set_trace, pytestPDB._pluginmanager)
     def fin():
@@ -38,6 +38,7 @@ def fin():
     pdb.set_trace = pytest.set_trace
     pytestPDB._pluginmanager = config.pluginmanager
     pytestPDB._config = config
+    pytestPDB._pdb_cls = pdb_cls
     config._cleanup.append(fin)
 
 class pytestPDB: