Find yaml and yml files using glob.glob()

Question

I'm struggling with finding yaml and yml files. What I want is to print two lists of files and check if there is any extra file. I can't figure out what is the regex of glob.glob

I did:

glob.glob('/data/config/**y*ml', recursive=True)))

But it's finding also xml files.

What I have right now is:

ymlFilenamesListA = sorted(map(os.path.basename, glob.glob('/data/config/**{yml,yaml}', recursive=True)))
ymlFilenamesListB = sorted(map(os.path.basename, glob.glob('/app/config/**{yml,yaml}', recursive=True)))
print(ymlFilenamesListA)
print(ymlFilenamesListB)

def compareList(l1,l2):
   l1.sort()
   l2.sort()
   if(l1==l2):
      return "No new files"
   else:
      print("Found new files: ")
      print(list(set(l1) - set(l2)))
      return sys.exit(1)

print(compareList(ymlFilenamesListA,ymlFilenamesListB))

And my output is:

./find.py
[]
[]
No new files

How can I compare two trees of files and check if there is any missing or some extra?