change loglevel to error for internal errors

When nose2 encounter an internal error, it swallows the stacktrace if
log level is not debug. To make debugging easier, change log level to
error.

nose2/main.py

@@ -108,7 +108,7 @@ def parseArgs(self, argv):
         """
         self.session = self.sessionClass()
         self.__class__._currentSession = self.session
-        
+
         self.argparse = self.session.argparse  # for convenience
 
         # XXX force these? or can it be avoided?
@@ -270,7 +270,7 @@ def runTests(self):
         try:
             self.result = runner.run(self.test)
         except Exception as e:
-            log.debug('Internal Error', exc_info=True)
+            log.exception('Internal Error')
             sys.stderr.write('Internal Error: runTests aborted: %s\n'%(e))
             if self.exit:
                 sys.exit(1)
@@ -287,7 +287,7 @@ def _makeRunner(self):
     @classmethod
     def getCurrentSession(cls):
         """Returns the current session, or ``None`` if no :class:`nose2.session.Session` is running.
-        
+
         """
         return cls._currentSession