is_token_expired buggy on non-UTC system

[joeb1415]

Describe the bug
is_token_expired() uses time.time() which returns system local time, which, when running on a non-UTC system, can return incorrectly.

Your code

token_info = auth_manager.cache_handler.get_cached_token()

print(f"Token expires_at:     {token_info['expires_at']}")
print(f"Local Time (Pacific): {int(time.time())}")
print(f"UTC Time:             {int(time.mktime(time.gmtime()))}")

# Token shows not expired, but it is expected that it is expired
print(auth_manager.is_token_expired(token_info))

Token expires_at:     1669239147
Local Time (Pacific): 1669229727
UTC Time:             1669247727
False

Expected behavior
Replace time.time() with, e.g., time.mktime(time.gmtime()) wherever used.

Environment:

• OS: Mac
• Python version: 3.6.8
• spotipy version: 2.21.0
• IDE: VSCode

Additional context
Add any other context about the problem here.

[stephanebruckert]

Great catch, would love a PR for it if you get a chance!