Bundle Install failed due to Sinatra dependencies

[l-espi]

Hello,

During the installation, the bundle install command inside the 'api' folder fails beacause Sinatra's dependency Mustermann needs a version of Ruby >= 2.2.0.

The gem install error is the following:

lms@lmsubuntu:~/livemediastreamerwebgui/api$ bundle install
Fetching gem metadata from https://rubygems.org/..........
Fetching version metadata from https://rubygems.org/...
Fetching dependency metadata from https://rubygems.org/..
Resolving dependencies...
Fetching mustermann 1.0.0
Installing mustermann 1.0.0
Fetching rack 2.0.3
Installing rack 2.0.3
Using tilt 2.0.7
Using yard 0.9.9
Fetching liquid 4.0.0
Installing liquid 4.0.0
Using kgio 2.11.0
Using raindrops 0.18.0
Using bson 4.2.2
Using bson_ext 1.5.1
Using mime-types 2.99.3
Using netrc 0.11.0
Using rmixer 0.0.1 from source at `../rmixer`
Using bundler 1.15.1
Gem::InstallError: mustermann requires Ruby version >= 2.2.0.
An error occurred while installing mustermann (1.0.0), and Bundler
cannot continue.
Make sure that gem install mustermann -v '1.0.0' succeeds before bundling.

In Gemfile:
  sinatra was resolved to 2.0.0, which depends on
    mustermann

I would like to know which Sinatra version was used originally, since the Gemfie doesn't seem to specify.

Thanks in advance.