解決方式：
把mysql的gem版本換成0.5.2
再bundle
bundle完之後再改回原本的版本就不影響團隊開發。
原則就是可以順利跑完bundle就好，暫時更改版號騙過bundle
Gemfile
gem "mysql2", "~> 0.5.2"
發生問題：
$ sudo gem install mysql2 -v 0.3.21
Building native extensions. This could take a while...
ERROR: Error installing mysql2:
ERROR: Failed to build gem native extension.
current directory: /Users/huyy01/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/mysql2-0.3.21/ext/mysql2
/Users/huyy01/.rbenv/versions/2.5.1/bin/ruby -r ./siteconf20180724-29825-pksvq0.rb extconf.rb
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
-----
Using mysql_config at /usr/local/bin/mysql_config
-----
checking for mysql.h... yes
checking for errmsg.h... yes
checking for mysqld_error.h... yes
-----
Setting rpath to /usr/local/Cellar/mysql/8.0.11/lib
-----
creating Makefile
current directory: /Users/huyy01/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/mysql2-0.3.21/ext/mysql2
make "DESTDIR=" clean
current directory: /Users/huyy01/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/mysql2-0.3.21/ext/mysql2
make "DESTDIR="
compiling client.c
client.c:439:3: error: use of undeclared identifier 'my_bool'
my_bool res = mysql_read_query_result(client);
^
client.c:441:19: error: use of undeclared identifier 'res'
return (void *)(res == 0 ? Qtrue : Qfalse);
^
client.c:762:3: error: use of undeclared identifier 'my_bool'
my_bool boolval;
^
client.c:793:7: error: use of undeclared identifier 'boolval'
boolval = (value == Qfalse ? 0 : 1);
^
client.c:794:17: error: use of undeclared identifier 'boolval'
retval = &boolval;
^
client.c:797:10: error: use of undeclared identifier 'MYSQL_SECURE_AUTH'; did you mean 'MYSQL_DEFAULT_AUTH'?
case MYSQL_SECURE_AUTH:
^~~~~~~~~~~~~~~~~
MYSQL_DEFAULT_AUTH
/usr/local/Cellar/mysql/8.0.11/include/mysql/mysql.h:188:3: note: 'MYSQL_DEFAULT_AUTH' declared here
MYSQL_DEFAULT_AUTH,
^
client.c:798:7: error: use of undeclared identifier 'boolval'
boolval = (value == Qfalse ? 0 : 1);
^
client.c:799:17: error: use of undeclared identifier 'boolval'
retval = &boolval;
^
client.c:830:38: error: use of undeclared identifier 'boolval'
wrapper->reconnect_enabled = boolval;
^
client.c:1185:38: error: use of undeclared identifier 'MYSQL_SECURE_AUTH'; did you mean 'MYSQL_DEFAULT_AUTH'?
return _mysql_client_options(self, MYSQL_SECURE_AUTH, value);
^~~~~~~~~~~~~~~~~
MYSQL_DEFAULT_AUTH
/usr/local/Cellar/mysql/8.0.11/include/mysql/mysql.h:188:3: note: 'MYSQL_DEFAULT_AUTH' declared here
MYSQL_DEFAULT_AUTH,
^
10 errors generated.
make: *** [client.o] Error 1
make failed, exit code 2
Gem files will remain installed in /Users/huyy01/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/mysql2-0.3.21 for inspection.
Results logged to /Users/huyy01/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/extensions/x86_64-darwin-17/2.5.0-static/mysql2-0.3.21/gem_make.out
sh-huyy01:redmine huyy01$ cd /Users/huyy01/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/