As mentioned in the earlier thread and possibly in someone's comment to issue #136:
I'm seeing the same kind of failure whenever I try to use --rpm-rpmbuild-define: The following runs fine if I simply remove the --rpm-rpmbuild-define parameter.
/usr/lib/ruby/gems/1.8/gems/fpm-0.4.13/lib/fpm/package/deb.rb:23: warning: already initialized constant COMPRESSION_TYPES
/usr/lib/ruby/gems/1.8/gems/fpm-0.4.13/lib/fpm/package/rpm.rb:45: undefined local variable or method `attributes' for #<FPM::Command:0x7f133289e558> (NameError)
from /usr/lib/ruby/gems/1.8/gems/clamp-0.3.1/lib/clamp/attribute_declaration.rb:32:in `instance_exec'
from /usr/lib/ruby/gems/1.8/gems/clamp-0.3.1/lib/clamp/attribute_declaration.rb:32:in `rpm_rpmbuild_define='
from /usr/lib/ruby/gems/1.8/gems/clamp-0.3.1/lib/clamp/option/parsing.rb:27:in `send'
from /usr/lib/ruby/gems/1.8/gems/clamp-0.3.1/lib/clamp/option/parsing.rb:27:in `parse_options'
from /usr/lib/ruby/gems/1.8/gems/clamp-0.3.1/lib/clamp/command.rb:49:in `parse'
from /usr/lib/ruby/gems/1.8/gems/clamp-0.3.1/lib/clamp/command.rb:63:in `run'
from /usr/lib/ruby/gems/1.8/gems/clamp-0.3.1/lib/clamp/command.rb:126:in `run'
from /usr/lib/ruby/gems/1.8/gems/fpm-0.4.13/bin/fpm:8
from /usr/bin/fpm:19:in `load'