Improve error message on DBI Exception

[sillitoe]

From Arun:

I have regenerated the xml file to have hierarchical id instead of the sun id. I am afraid, I am getting errors when I tried the following

./genome3d-api -o updateDomainPrediction -u V5QRX7 -r SUPERFAMILY --xmlfile=../tuberculosis/V5QRX7.xml

It produced the following error

Mon Jul 23 16:11:31 2018   INFO | APP.OPENAPI_SPEC               http://daily.genome3d.eu/api/openapi.json
Mon Jul 23 16:11:31 2018   INFO | APP.MODE                       DAILY
Mon Jul 23 16:11:31 2018   INFO | REQUEST.OPERATION              updateDomainPrediction
Mon Jul 23 16:11:31 2018   INFO | REQUEST.DATA                   {"resource_id":"SUPERFAMILY","operation":"updateDomainPrediction","xmlfile":[{"file":"../tuberculosis/V5QRX7.xml"}],"uniprot_acc":"V5QRX7"}
Mon Jul 23 16:11:31 2018   INFO | REQUEST.URL                    http://daily.genome3d.eu/api/v1/uniprot/V5QRX7/domain_prediction/SUPERFAMILY
[400] ERROR: Bad Request ({"message":"DBIx::Class::Storage::DBI::_dbh_execute(): DBI Exception: DBD::Pg::st execute failed: ER...)

[sillitoe]

Looks like the actual error is being caused by a permissions issue at my end (see #5)

This has been "improved" simply by making the error message longer (and fixing the actual error).

I think that's okay for the moment.