Fix Python 3 issues

* Fix print syntax in check_valid_gerrit_projects.py
* tox.ini: jenkins-project env works also on Python 3, no need to force
  Python 2.7

Change-Id: I3c643470c6b5db666aeab208c615382719f8768d

tools/check_valid_gerrit_projects.py

@@ -50,7 +50,7 @@ for p in projects:
         print("Error: Entry is not a project %s" % p)
         continue
     if args.verbose:
-        print 'Checking %s' % (name)
+        print('Checking %s' % name)
     description = p.get('description')
     if not description and repo_group in DESCRIPTION_REQUIRED:
         found_errors += 1

tox.ini

@@ -52,7 +52,6 @@ commands =
   jenkins-jobs -l debug test -o {envdir}/tmp jenkins/jobs
 
 [testenv:jenkins-project]
-basepython = python2.7
 deps =
 commands =
   {toxinidir}/tools/jenkins-projects-checks.py