Move write_pbr_json to avoid issues with nose

Put write_pbr_json in pbr.pbr_json so that you do not need to import
pbr.packaging to use it. This avoids python3 errors with nose where nose
is imported by pbr before it is converted to python3 by 2to3 under
python3.

Change-Id: I1c420fed609bc60bbfdf78eb219e067ccab1a61e

pbr/packaging.py

@@ -25,7 +25,6 @@ from distutils import log
 import email
 import functools
 import itertools
-import json
 import os
 import platform
 import re
@@ -41,6 +40,7 @@ from setuptools.command import sdist
 from pbr import extra_files
 from pbr import git
 from pbr import options
+import pbr.pbr_json
 from pbr import version
 
 REQUIREMENTS_FILES = ('requirements.txt', 'tools/pip-requires')
@@ -505,19 +505,6 @@ def _get_increment_kwargs(git_dir, tag):
     return result
 
 
-def write_pbr_json(cmd, basename, filename):
-    git_dir = git._run_git_functions()
-    if not git_dir:
-        return
-    values = dict()
-    git_version = git.get_git_short_sha(git_dir)
-    is_release = git.get_is_release(git_dir)
-    if git_version is not None:
-        values['git_version'] = git_version
-        values['is_release'] = is_release
-        cmd.write_file('pbr', filename, json.dumps(values))
-
-
 def _get_revno_and_last_tag(git_dir):
     """Return the commit data about the most recent tag.
 
@@ -671,3 +658,10 @@ def get_version(package_name, pre_version=None):
     raise Exception("Versioning for this project requires either an sdist"
                     " tarball, or access to an upstream git repository."
                     " Are you sure that git is installed?")
+
+
+# This is added because pbr uses pbr to install itself. That means that
+# any changes to the egg info writer entrypoints must be forward and
+# backward compatible. This maintains the pbr.packaging.write_pbr_json
+# path.
+write_pbr_json = pbr.pbr_json.write_pbr_json

pbr/pbr_json.py

@@ -0,0 +1,32 @@
+# Copyright 2011 OpenStack LLC.
+# Copyright 2012-2013 Hewlett-Packard Development Company, L.P.
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import json
+
+from pbr import git
+
+
+def write_pbr_json(cmd, basename, filename):
+    git_dir = git._run_git_functions()
+    if not git_dir:
+        return
+    values = dict()
+    git_version = git.get_git_short_sha(git_dir)
+    is_release = git.get_is_release(git_dir)
+    if git_version is not None:
+        values['git_version'] = git_version
+        values['is_release'] = is_release
+        cmd.write_file('pbr', filename, json.dumps(values))

setup.cfg

@@ -39,7 +39,7 @@ distutils.setup_keywords =
 distutils.commands =
     testr = pbr.testr_command:Testr
 egg_info.writers =
-    pbr.json = pbr.packaging:write_pbr_json
+    pbr.json = pbr.pbr_json:write_pbr_json
 console_scripts =
     pbr = pbr.cmd.main:main