Make argument type error messages use __str__ method of Predicates

[gmarceau]

Previous behavior looks like this

Error: Argument of output expected to be <plumbum.cli.switches.Predicate object at 0x10ce91c10>, not 'requirements.txt':
        ValueError('output is a file, should be a directory',)

now looks like this

    Error: Argument of output expected to be 'MakeDirectory', not 'requirements.txt':
        ValueError('output is a file, should be a directory',)

when checking a Predicate.

[henryiii]

Would you mind changing this to use "{0} {1}".format() style or "{val} {other}".format() style? I'd prefer that going forward.

[henryiii]

Something like:

raise WrongArgumentType("Argument of {name} expected to be {argtype}, not {val!r}:\n    {ex!r}".format(
                    name=name, argtype=argtype, val=val, ex=ex))

[gmarceau]

That works

[henryiii]

As soon as Travis finishes, I'll accept.

[gmarceau]

We've been using a ton of plumbum at bodylabs. It is replacing both our usages of argparse and of Bash, no less. Thank you for creating it.

[coveralls]

Coverage decreased (-0.4%) to 80.899% when pulling 619b354 on bodylabs:use_predicate___str__ into 67b25df on tomerfiliba:master.

[coveralls]

Coverage decreased (-0.4%) to 80.899% when pulling 619b354 on bodylabs:use_predicate___str__ into 67b25df on tomerfiliba:master.

[coveralls]

Coverage remained the same at 81.258% when pulling 9d241e4 on bodylabs:use_predicate___str__ into 67b25df on tomerfiliba:master.

[coveralls]

Coverage decreased (-0.4%) to 80.899% when pulling 9d241e4 on bodylabs:use_predicate___str__ into 67b25df on tomerfiliba:master.

[coveralls]

Coverage decreased (-0.4%) to 80.899% when pulling 9d241e4 on bodylabs:use_predicate___str__ into 67b25df on tomerfiliba:master.

[coveralls]

Coverage decreased (-0.4%) to 80.899% when pulling 9d241e4 on bodylabs:use_predicate___str__ into 67b25df on tomerfiliba:master.