Various checksum improvements

[intgr]

I found three things to quibble about in the checksum implementation, here is the PR.

Long story short, it always bothered me when people write checksum code in such "magic" fashion, comparing the end result with a constant. But in this case it's an actual bug: checksum values '00', '01' and '99' can never occur in valid IBAN numbers, but previously the value 'EE012200221111099080' for example was accepted.

3rd commit refactors the checksum out into a separate function, I found that useful when converting legacy Estonian account numbers to IBAN format. This builds on changes made in the 1st commit.

[coveralls]

Coverage increased (+0.04%) when pulling 11cd9ff on intgr:checksum into 47e72fe on benkonrath:master.

[coveralls]

Coverage increased (+0.04%) when pulling 226feb7 on intgr:checksum into 47e72fe on benkonrath:master.

[benkonrath]

Thanks for the PR. I'm no longer taking pull requests for the IBAN code in this repo as the code has now been contributed to django-localflavor. I will be deprecating this package as soon as the BICField is merged there as well.

I haven't actually looked at this PR but I think it's better to discuss this as part of an improvement to django-localflavor. Can you re-do this PR against the code there? Thanks.

https://github.com/django/django-localflavor

[intgr]

Sure, thanks. Could you perhaps change the project description and/or README to say explicitly that this project is deprecated?

[benkonrath]

The package won't be depreciated the BICField is merged in django-localflavor.

[benkonrath]

Also the IBAN fields aren't in a released version of django-localflavor yet. As soon as this happens, I'll officially depreciate this module and provide migration instructions.

[benkonrath]

I ended up adding a pointer to django-localflavor in the development section of the README. Thanks for the suggestion. I have commit access to django-localflavor so I can review your PR there.

[intgr]

Thanks!