Error when adding an AWS host

From /var/log/one/oned.log:

/usr/share/ruby/psych.rb:205:in parse': (<unknown>): found character that cannot start any token while scanning for the next token at line 11 column 1 (Psych::SyntaxError) from /usr/share/ruby/psych.rb:205:inparse_stream’
from /usr/share/ruby/psych.rb:153:in parse' from /usr/share/ruby/psych.rb:129:inload’
from /usr/lib/one/ruby/ec2_driver.rb:215:in initialize' from ./poll:33:innew’
from ./poll:33:in `'
ERROR MESSAGE --8<------
Error executing poll
ERROR MESSAGE ------>8–

I have tried:

gem install aws-sdk-v1

gem uninstall aws-sdk

and re-installing gems:

/usr/share/one/install_gems

The error indicates that the syntax of /etc/one/ec2_driver_conf is wrong. Please validate that the document conforms with the yaml syntax.