Use importlib for versioning

The semver parsing in PBR doesn't handle the full suite of pep440
versions (for example: 1.2.3+foo1 is the pep440 recommended way
of handling local versions).

Since we aren't doing anything with the parsed versions anyway,
just return the string we get from importlib.

Change-Id: I0a838c639333c40db5b12cd852b921f1b1c87fed

nodepool/cmd/__init__.py

@@ -26,7 +26,7 @@ import sys
 import threading
 import traceback
 
-from nodepool.version import version_info as npd_version_info
+from nodepool.version import release_string
 from nodepool import logconfig
 
 yappi = extras.try_import('yappi')
@@ -130,7 +130,7 @@ class NodepoolApp(object):
         return os.path.abspath(os.path.expanduser(path))
 
     def _get_version(self):
-        return "Nodepool version: %s" % npd_version_info.release_string()
+        return "Nodepool version: %s" % release_string
 
     def create_parser(self):
         parser = argparse.ArgumentParser(

nodepool/driver/openstack/adapter.py

@@ -504,7 +504,7 @@ class OpenStackAdapter(statemachine.Adapter):
             use_direct_get=False,
             rate_limit=rate_limit,
             app_name='nodepool',
-            app_version=version.version_info.version_string()
+            app_version=version.release_string
         )
 
     def _submitApi(self, api, *args, **kw):

nodepool/version.py

@@ -14,11 +14,10 @@
 
 import json
 
-import pbr.version
+from importlib import metadata as importlib_metadata
 import pkg_resources
 
-version_info = pbr.version.VersionInfo('nodepool')
+release_string = importlib_metadata.distribution('nodepool').version
-release_string = version_info.release_string()
 
 is_release = None
 git_version = None