misc: adapt version number for PEP 440 (#29421)

setup.py

@@ -73,9 +73,18 @@ def get_version():
                              stderr=subprocess.PIPE)
         result = p.communicate()[0]
         if p.returncode == 0:
-            version = str(result.split()[0][1:])
-            version = version.replace('-', '.')
+            result = result.decode('ascii').strip()[1:]  # strip spaces/newlines and initial v
+            if '-' in result:  # not a tagged version
+                real_number, commit_count, commit_hash = result.split('-', 2)
+                version = '%s.post%s+%s' % (real_number, commit_count, commit_hash)
+            else:
+                version = result
             return version
+        else:
+            return '0.0.post%s' % len(
+                    subprocess.check_output(
+                            ['git', 'rev-list', 'HEAD']).splitlines())
+
     return '0.0.0'
 
 setuptools.setup(