The above method didn’t work for me.
I kept getting incorrect header check (Zlib::DataError) error. Apparently it assumes you have a header by default, which may not always be the case.
The work around that I implemented was:
require 'zlib'
require 'stringio'
gz = Zlib::GzipReader.new(StringIO.new(resp.body.to_s))
uncompressed_string = gz.read