我已经在Stackoverflow.com上查看并尝试了有关该主题的所有内容，但仍然无法弄清楚……
当我'gem install mysql2'时，出现权限错误。当我'sudo gem install mysql2'我得到以下信息：
Teds-MacBook-Pro:~ tedmartin$ sudo gem install mysql2
Building native extensions. This could take a while...
ERROR: Error installing mysql2:
ERROR: Failed to build gem native extension.
current directory: /Users/tedmartin/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/mysql2-0.4.5/ext/mysql2
/Users/tedmartin/.rbenv/versions/2.4.1/bin/ruby -r ./siteconf20170420-50202-1nekuvd.rb extconf.rb
checking for rb_absint_size()... yes
checking for rb_absint_singlebit_p()... yes
checking for ruby/thread.h... yes
checking for rb_thread_call_without_gvl() in ruby/thread.h... yes
checking for rb_thread_blocking_region()... no
checking for rb_wait_for_single_fd()... yes
checking for rb_hash_dup()... yes
checking for rb_intern3()... yes
checking for rb_big_cmp()... yes
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Using mysql_config …