velin . --check throws an undefined variable error

[ianhi]

This needs_changes is never defined:

velin/velin/ref.py

Lines 760 to 767 in 203568d

	f.write(new)
	if args.check:
	if need_changes:
	sys.exit(
	"Some files/functions need updates:\n - " + "\n - ".join(need_changes)
	)
	else:
	sys.exit(0)

which causes velin . --check to fail:

Traceback (most recent call last):
  File "/home/ian/mambaforge/envs/micro/bin/velin", line 8, in <module>
    sys.exit(main())
  File "/home/ian/mambaforge/envs/micro/lib/python3.8/site-packages/velin/ref.py", line 762, in main
    if need_changes:
NameError: name 'need_changes' is not defined

though there is a commented out definition a few lines above

velin/velin/ref.py

Line 722 in 203568d

# need_changes = []