cannot install due missing aws-sdk-core version

[glasswalk3r]

During a new setup to run my specs:

bundle config set --local path '.vendor'
bundle install
Fetching gem metadata from https://rubygems.org/
Fetching gem metadata from https://rubygems.org/.........
Could not find aws-sdk-core-3.121.4 in any of the sources
make: *** [Makefile:39: test-init] Error 7

Looking at the rubygems.org, it seems this specific version was "yanked" (whatever that means).
An workaround it to upgrade all dependencies, but that might brake awspec due API changes. At least for my specs, everything worked just fine.