I run TracksApp on an older version of Ubuntu and upgrading from 2.1 to 2.1.1 failed at the bundle install step with:
Installing mysql (2.9.0) with native extensions
Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers. Check the mkmf.log file for more
details. You may need configuration options.
Gem files will remain installed in /home/conficio/.bundler/tmp/2409/gems/mysql-2.9.0 for inspection.
Results logged to /home/conficio/.bundler/tmp/2409/gems/mysql-2.9.0/ext/mysql_api/gem_make.out
An error occurred while installing mysql (2.9.0), and Bundler cannot continue.
Make sure that `gem install mysql -v '2.9.0'` succeeds before bundling.
The cause is an added dependency on libmysqlclient-dev, which is easily solved by
$ sudo sudo apt-get install libmysqlclient-dev