Bundler could not find compatible versions for gem “bundler”: In Gemfile:

在運行jekyll server 的時候遇到的坑：

Fetching gem metadata from https://gems.ruby-china.com/...........
Fetching gem metadata from https://gems.ruby-china.com/.
Resolving dependencies...
Bundler could not find compatible versions for gem "bundler":
  In Gemfile:
    bundler (~> 1.12) x64-mingw32

  Current Bundler version:
    bundler (2.1.4)
This Gemfile requires a different version of Bundler.
Perhaps you need to update Bundler by running `gem install bundler`?

Could not find gem 'bundler (~> 1.12)' in any of the relevant sources:
  the local ruby installation

原因是bundler version 2.1.4, 但是這個jekyll主題用的bundler version 1.12。所以要降級：

$ gem install bundler -v 1.12
$ bundle _1.12_ install