gauntlt-docker - gives No files found - file present int the current directory

[pradeepn-altran]

./gauntlt-docker ./xss.attack
[DEPRECATION] The trollop gem has been renamed to optimist and will no longer be supported. Please switch to optimist as soon a
s possible.
/var/lib/gems/2.3.0/gems/gauntlt-1.0.13/lib/gauntlt/runtime.rb:20:in initialize': No files found in path: ./xss.attack (Gauntl t::Runtime::NoFilesFound) from /var/lib/gems/2.3.0/gems/gauntlt-1.0.13/lib/gauntlt/attack.rb:8:in new'
from /var/lib/gems/2.3.0/gems/gauntlt-1.0.13/lib/gauntlt/attack.rb:8:in initialize' from /var/lib/gems/2.3.0/gems/gauntlt-1.0.13/lib/gauntlt.rb:36:in new'
from /var/lib/gems/2.3.0/gems/gauntlt-1.0.13/lib/gauntlt.rb:36:in attack' from /var/lib/gems/2.3.0/gems/gauntlt-1.0.13/bin/gauntlt:55:in <top (required)>'
from /usr/local/bin/gauntlt:23:in load' from /usr/local/bin/gauntlt:23:in

'