Clarify UIntBase error message

[ixje]

What current issue(s) does this address?, or what feature is it adding?
This one has been bothering me for a while so it's about time to clarify it. The error message when providing data that is not long enough is not self explanatory.

UInt256(data=bytearray.fromhex('aabb'))
UInt256(data=b'aa' * 32)

both produce

Invalid UInt

A more verbose error message can clarify what is wrong about the data.

How did you solve this problem?
make the error message more verbose.

Case 1

Invalid UInt - data length 2 != specified num_bytes 32

It's immediately clear I'm not providing enough data

Case 2

Invalid UInt - data length 64 != specified num_bytes 32

It becomes clear that the format I'm providing data in isn't valid and I have to convert it to raw bytes.

How did you make sure your solution works?
ran some manual tests in Ipython.

Did you add any tests?
no

Are there any special changes in the code that we should be aware of?
no

[coveralls]

Coverage remained the same at 100.0% when pulling 4726ce7 on ixje:clarify_uintbase_error into 191cca8 on CityOfZion:master.

[metachris]

Nice. I'd use Invalid UInt: data length instead of -.

[localhuman]

Change message to Invalid UInt: data length ...

[coveralls]

Coverage remained the same at 100.0% when pulling 4726ce7 on ixje:clarify_uintbase_error into 191cca8 on CityOfZion:master.