Improve error message
Improve error message

Old message:
&{%!s(token.Pos=1478849) %!s(*ast.FieldList=&{1478853 [0xc8217db440] 1478870}) %!s(*ast.FieldList=&{1478872 [0xc8217db480 0xc8217db4c0] 1478888})} is unsupported for a schema

New message:
Expr (/home/dng/support-ticket-service/app/src/gopkg.in/mgo.v2/session.go:386:13) is unsupported for a schema
lhdomenech/go-swagger,ThalesIgnite/go-swagger,go-swagger/go-swagger,gaplyk/go-swagger,jakedsouza/go-swagger,pieter-lazzaro/go-swagger,kayla90/go-swagger,galaxie/go-swagger,nelz9999/go-swagger,jakedsouza/go-swagger,go-swagger/go-swagger,gaplyk/go-swagger,lhdomenech/go-swagger,pieter-lazzaro/go-swagger,nelz9999/go-swagger,ThalesIgnite/go-swagger,galaxie/go-swagger,kayla90/go-swagger