"RuntimeError : Don't know how to build task './build.yaml'"

After adding the build.yaml file to specify configuration options, we discover a problem related with relative path on some files like build.yaml or files under tasks directory like tasks/*.rake.

We add some expand_atabs to application.rb to fix it.

This is the callchain

RuntimeError : Don't know how to build task './build.yaml'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/1.9.1/rake.rb:1721:in `[]'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/test.rb:562:in `block in needed?'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/test.rb:562:in `map'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/test.rb:562:in `needed?'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/1.9.1/rake.rb:613:in `format_trace_flags'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/application.rb:661:in `block in invoke_with_call_chain'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/1.9.1/monitor.rb:201:in `mon_synchronize'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/application.rb:659:in `invoke_with_call_chain'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/application.rb:654:in `invoke'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/test.rb:164:in `block (2 levels) in run_local_tests'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/test.rb:161:in `each'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/test.rb:161:in `block in run_local_tests'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/project.rb:351:in `[]'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/project.rb:351:in `block in local_projects'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/project.rb:351:in `each'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/project.rb:351:in `local_projects'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/test.rb:158:in `run_local_tests'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/test.rb:624:in `block (2 levels) in <module:Test>'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/1.9.1/rake.rb:634:in `call'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/1.9.1/rake.rb:634:in `block in execute'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/1.9.1/rake.rb:629:in `each'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/1.9.1/rake.rb:629:in `execute'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/application.rb:673:in `block in invoke_with_call_chain'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/1.9.1/monitor.rb:201:in `mon_synchronize'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/application.rb:659:in `invoke_with_call_chain'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/application.rb:654:in `invoke'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/1.9.1/rake.rb:2042:in `invoke_task'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/application.rb:246:in `block (2 levels) in top_level'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/application.rb:246:in `each'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/application.rb:246:in `block in top_level'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/application.rb:534:in `standard_exception_handling'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/application.rb:237:in `top_level'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/application.rb:138:in `block in run'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/application.rb:534:in `standard_exception_handling'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/lib/buildr/core/application.rb:135:in `run'
/tsp/projects/sapc_CBA/design/environment/ruby-1.9.2-p180/lib/ruby/gems/1.9.1/gems/buildr-1.4.6/bin/buildr:19:in `<top (required)>'
/tsp/projects/sapc_CBA/design/environment//ruby-1.9.2-p180//bin//buildr:23:in `load'
/tsp/projects/sapc_CBA/design/environment//ruby-1.9.2-p180//bin//buildr:23:in `<main>'