update backtrace string format regex

[keepcosmos]

Every backtrace strings do not include :in
http://ruby-doc.org/core-1.9.3/Exception.html#method-i-backtrace

[rails-bot]

Thanks for the pull request, and welcome! The Rails team is excited to review your changes, and you should hear from @jonleighton (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

[grosser]

we can simplify this to: line[/^(.*)\:\d+/, 1]

[grosser]

can you reproduce a trace without the in ?

[keepcosmos]

@grosser
backtrace can override.
Actually, I found overrided #backtrace method in 126 line of https://github.com/sass/sass/blob/stable/lib/sass/error.rb

Ruby 1.9 document said,
The backtrace is an array of strings, each containing either “filename:lineNo: in method”‘ or “filename:lineNo.”
http://ruby-doc.org/core-1.9.3/Exception.html#method-i-backtrace
We can not sure bracktrace strings match with /^(.*)\:\d+\:in /

[grosser]

thx, 1.6.1 is out

[keepcosmos]

@grosser Thanks ❤️