[Rspec-devel] Failure messages - customize per "should"assertion

[itsme213]

> part 2: This is the failed should_*. The purpose is to communicate the
> detailed information about it, such as why something failed and where
> (line number).

The line_number is necessary not always sufficient. In the same spirit as 
generating user-readable narrative specs from spec, we might aim for 
user-readable spec-failure reports, which could need more dynamic context 
than a static "specify" string can provide.