Change StatementError formatting (newlines and %s)

Change StatementError formatting (newlines and %s)

This changes the error formatting for StatementError in two ways:

1) Break each error detail up over multiple newlines instead of
   spaced out on a single line. Hopefully, this helps readers scan
   the error message more easily.

2) Change the SQL representation in the message to use __str__ (%s)
   instead of the current behavior that uses __repr__ (%r). This
   should help readers recognize the structure of their SQL,
   particularly if it is a multiline SQL statement. In the multiline
   case, the SQL would be printed over multiple lines instead of
   printing an escaped "\n".