gistfile1.txt

Fatal error: Uncaught exception 'RuntimeException' with message '/Users/igor/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/1.9.1/rubygems.rb:762:in `report_activate_error': Could not find RubyGem sass (>= 0) (Gem::LoadError)
	from /Users/igor/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/1.9.1/rubygems.rb:219:in `activate'
	from /Users/igor/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/1.9.1/rubygems.rb:1065:in `gem'
	from /Users/igor/.rvm/gems/ruby-1.9.2-p0/bin/sass:18:in `<main>'
' in /Users/igor/Sites/silex-assetic/vendor/assetic/src/Assetic/Filter/Sass/SassFilter.php:167
Stack trace:
#0 /Users/igor/Sites/silex-assetic/vendor/assetic/src/Assetic/Filter/FilterCollection.php(57): Assetic\Filter\Sass\SassFilter->filterLoad(Object(Assetic\Asset\FileAsset))
#1 /Users/igor/Sites/silex-assetic/vendor/assetic/src/Assetic/Asset/BaseAsset.php(71): Assetic\Filter\FilterCollection->filterLoad(Object(Assetic\Asset\FileAsset))
#2 /Users/igor/Sites/silex-assetic/vendor/assetic/src/Assetic/Asset/FileAsset.php(41): Assetic\Asset\BaseAsset->doLoad('body {??backgro...', in /Users/igor/Sites/silex-assetic/vendor/assetic/src/Assetic/Filter/Sass/SassFilter.php on line 167

gistfile2.php

<?php

    $app['assetic.filter_manager']->set('scss',
        new Assetic\Filter\Sass\ScssFilter($app['assetic.path'], '/Users/igor/.rvm/gems/ruby-1.9.2-p0/bin/sass'));
    
    // factory
    $css = $app['assetic']->createAsset(array(
        'css/*.scss',
    ), array(
        'scss',
    ));
    
    echo $css->dump();

You should wrap the asset returned by createAsset() in an instance of AssetCache and use HTTP caching, btw. See here.

@igorw I've got the same problem right now, on ubuntu with rvm. Dis you manage to solve this problem?

I did not, I'm afraid.

do you think that this is a ruby problem, an assetic problem, or a problem with the integration of assetic with ruby?
I use it with compass anyway...but the error is identical.
If i install rubygems via software center it works...but rvm is faster, and allow me to have different ruby+gems configuration.

In my case the cause for it was RVM doing some path magic that was ignored by the exec stuff used by assetic.

YAY!
Just found a solution!
You just need to create a wrapper script to load the ruby environment. Mine is:

#!/bin/bash
source "/usr/share/ruby-rvm/environments/ruby-1.9.2-p290"
exec compass "$@"

I place it in /usr/bin/compass and make it executable.
source: http://www.phphosts.org/blog/2011/03/how-to-use-rvm-installs-of-ruby-in-shell-cgi-scripts/