Fix overly-broad exception expectations in tests

[jkeifer]

(This is part of work currently staged on #268.)

We are ignoring the linter rules B017 and PT011 in test files. These flag overly-broad exceptions in pytest.raises() calls, which is a problem as unexpected things could go wrong in the code and be missed.

We need to remove the ignores for those rules and audit/fix each flagged occurrence.