How to install sensu from source code ?

Hi,

Anyone here can help me ?

I want to add some code to sensu, so I download sensu code from github, and did some changes.
Then, I googled a little, and found some commands. But all these commands return with error, for example:

gem build sensu.gemspec

Invalid gemspec in [sensu.gemspec]: can’t modify frozen String

ERROR: Error loading gemspec. Aborting.

Or:

bundle install

[!] There was an error parsing Gemfile:

[!] There was an error while loading sensu.gemspec: can’t modify frozen String. Bundler cannot continue.

from /opt/stack/sensu/sensu.gemspec:6

-------------------------------------------

s.name = “sensu”

s.version = Sensu::VERSION

s.authors = [“Sean Porter”, “Justin Kolberg”]

-------------------------------------------

. Bundler cannot continue.

from /opt/stack/sensu/Gemfile:3

-------------------------------------------

···

gemspec

-------------------------------------------

Thanks,

-chen