fixed bug when set a local cache_path in BaseMacLookup

[mh4x0f]

when we load a custom cache_path file from my machine i got errors. for this example bellow, the app crash:

from mac_vendor_lookup import MacLookup, BaseMacLookup

BaseMacLookup.cache_path = "/home/storage/mac-vendors.txt"
mac = MacLookup()
    
def find_mac(mac_address):
    print(mac.lookup(mac_address))

my patch solve this problem. thanks

[tomerkal]

The change you're suggesting breaks the current assumption that update_vendors writes to the cache file lines in the format of <prefix>:<vendor>.
What happened is that you probably loaded the OUI file directly to the cache path, which is wrong. You then got errors because there are no : in most lines and the load_vendors logic broke. If you want to manually update the cached list, it needs to follow the : line structure.
Anyway, the change proposed here will lead to errors (update_vendors writes the cache with the : format, the your suggested load_vendors tries to read the same file with the (base 16) format).