calcs/risk/base:

Added a better error message for `check_imts`.
tests/calcs/risk/classical/core_test:

Updated a test (per changes in the code) so that we don't get unicode
artifacts when casting a list to a str.
Merge pull request #1185 from larsbutler/unicode-list-cast-fix

Unicode list cast fix

[r=matley] [f=*trivial]