Print expected type instead of its string representation

[trishankkarthik]

Observed

Presently, if a user passes an object O other a list to a Schema ListOf object, the error message will print the string representation S of O. Unfortunately, the error message is obscured when the S is large (e.g. O is a set with hundreds of thousands of strings).

Expected

I think the error message would be just as effective if we simply printed the type of O.

Thanks!

[joshuagl]

Schema objects were moved to securesystemslib, but this issue is replicated in the new location.
ListOf's check_match prints the repr() of the object, not the type() see schema.py:523

PR #794 was closed without comment, is this change desirable? Or should we just close this issue?

[trishankatdatadog]

Moved to securesystemslib