Ignore non-version milestones

README.md

@@ -3,6 +3,9 @@
 This action attaches the next open milestone to a given PR, if that PR
 was merged.
 
+Currently, this action only looks at milestones that can be parsed as
+version numbers.
+
 A typical job would look like this:
 
 ```yaml

next-milestone.py

@@ -1,17 +1,27 @@
 import requests
 import argparse
-from packaging.version import Version
+from packaging.version import Version, InvalidVersion
 
 parser = argparse.ArgumentParser()
 parser.add_argument('owner_repo')
 args = parser.parse_args()
 
 owner, repo = args.owner_repo.split('/')
 
+
+def is_version(v):
+    try:
+        Version(v)
+        return True
+    except InvalidVersion:
+        return False
+
+
 # Get the list of milestones for the repository
 milestones_url = f'https://api.github.com/repos/{owner}/{repo}/milestones'
 response = requests.get(milestones_url)
 milestones = response.json()
+milestones = [m for m in milestones if is_version(m['title'])]
 milestones = sorted(milestones, key=lambda x: Version(x['title']))
 
 print(milestones[0]['number'])