1 files changed, 20 insertions, 21 deletions

diff --git a/lib/spack/external/_pytest/debugging.py b/lib/spack/external/_pytest/debugging.py
index d96170bd8b..aa9c9a3863 100644
--- a/lib/spack/external/_pytest/debugging.py
+++ b/lib/spack/external/_pytest/debugging.py
@@ -1,10 +1,8 @@
 """ interactive debugging with PDB, the Python Debugger. """
-from __future__ import absolute_import
+from __future__ import absolute_import, division, print_function
 import pdb
 import sys
 
-import pytest
-
 
 def pytest_addoption(parser):
     group = parser.getgroup("general")
@@ -16,19 +14,17 @@ def pytest_addoption(parser):
         help="start a custom interactive Python debugger on errors. "
              "For example: --pdbcls=IPython.terminal.debugger:TerminalPdb")
 
-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)
 
@@ -37,30 +33,33 @@ def pytest_configure(config):
         pytestPDB._config = None
         pytestPDB._pdb_cls = pdb.Pdb
 
-    pdb.set_trace = pytest.set_trace
+    pdb.set_trace = pytestPDB.set_trace
     pytestPDB._pluginmanager = config.pluginmanager
     pytestPDB._config = config
+    pytestPDB._pdb_cls = pdb_cls
     config._cleanup.append(fin)
 
+
 class pytestPDB:
     """ Pseudo PDB that defers to the real pdb. """
     _pluginmanager = None
     _config = None
     _pdb_cls = pdb.Pdb
 
-    def set_trace(self):
+    @classmethod
+    def set_trace(cls):
         """ invoke PDB set_trace debugging, dropping any IO capturing. """
         import _pytest.config
         frame = sys._getframe().f_back
-        if self._pluginmanager is not None:
-            capman = self._pluginmanager.getplugin("capturemanager")
+        if cls._pluginmanager is not None:
+            capman = cls._pluginmanager.getplugin("capturemanager")
             if capman:
                 capman.suspendcapture(in_=True)
-            tw = _pytest.config.create_terminal_writer(self._config)
+            tw = _pytest.config.create_terminal_writer(cls._config)
             tw.line()
             tw.sep(">", "PDB set_trace (IO-capturing turned off)")
-            self._pluginmanager.hook.pytest_enter_pdb(config=self._config)
-        self._pdb_cls().set_trace(frame)
+            cls._pluginmanager.hook.pytest_enter_pdb(config=cls._config)
+        cls._pdb_cls().set_trace(frame)
 
 
 class PdbInvoke:
@@ -74,7 +73,7 @@ class PdbInvoke:
 
     def pytest_internalerror(self, excrepr, excinfo):
         for line in str(excrepr).split("\n"):
-            sys.stderr.write("INTERNALERROR> %s\n" %line)
+            sys.stderr.write("INTERNALERROR> %s\n" % line)
             sys.stderr.flush()
         tb = _postmortem_traceback(excinfo)
         post_mortem(tb)