fix internal server error when logging parse-time exceptions w/ unicode values
fix internal server error when logging parse-time exceptions w/ unicode values

Errors such as "unknown schema" with a unicode schema name could cause
an internal server error due to naive interpolation into an ASCII error
message template during logging... this caused a 500 response when it
should have logged the stack and continued with a 409 response.

informatics-isi-edu/ermrest,informatics-isi-edu/ermrest