Make setup.py find the version in azure pipelines

setup.py

@@ -6,9 +6,11 @@
 # For development and local builds use this version number, but for real builds replace it
 # with the tag found in the environment
 package_version = "4.0.0.dev0"
-for variable_name in ['BITBUCKET_TAG']:
-    package_version = os.environ.get(variable_name, package_version)
-    package_version = package_version.lstrip('v')
+if 'BITBUCKET_TAG' in os.environ:
+    package_version = os.environ['BITBUCKET_TAG'].lstrip('v')
+elif 'BUILD_SOURCEBRANCH' in os.environ:
+    full_tag_prefix = 'refs/tags/v'
+    package_version = os.environ['BUILD_SOURCEBRANCH'][len(full_tag_prefix):]
 
 
 setup(