pytest: use ipdb as default --pdb handler

pytest.ini

@@ -1,11 +1,15 b''
 [pytest]
 testpaths = ./rhodecode
 pylons_config = rhodecode/tests/rhodecode.ini
 vcsserver_protocol = http
 vcsserver_config_http = rhodecode/tests/vcsserver_http.ini
 norecursedirs = tests/scripts
-addopts = -k "not _BaseTest"
+
+addopts =
+  -k "not _BaseTest"
+  --pdbcls=IPython.terminal.debugger:TerminalPdb
+
 markers =
   vcs_operations: Mark tests depending on a running RhodeCode instance.
   xfail_backends: Mark tests as xfail for given backends.
   skip_backends: Mark tests as skipped for given backends.