我正在尝试使用Taps gem将现有的sqlite 3 db迁移到Rails中的Postgresql。但是，当我尝试运行“ taps服务器”命令时，总是会出错。
我曾尝试将机架的版本更改为1.0.1，并尝试在rvm上安装ruby 2.0.0，因为我读到这也可能是机架不起作用的原因。
Database.yml：
development:
adapter: postgresql
encoding: unicode
database: ottom8_development
pool: 5
username: gbade
password:
test:
adapter: postgresql
encoding: unicode
database: ottom8_test
pool: 5
username: gbade
password:
production:
adapter: postgresql
encoding: unicode
database: ottom8_production
pool: 5
username: gbade
password:
当我在终端中使用此命令时，
$ taps server sqlite://db/development.sqlite3 gbade cucumber
我收到此错误
/Users/gbade/.rvm/gems/ruby-2.4.1/gems/sequel-
3.20.0/lib/sequel/database/schema_generator.rb:19: warning: constant
::Fixnum is deprecated
/Users/gbade/.rvm/gems/ruby-2.4.1/gems/sequel-
3.20.0/lib/sequel/database/schema_generator.rb:19: warning: constant
::Bignum is deprecated
/Users/gbade/.rvm/rubies/ruby-2.4.1/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:133:in `require': cannot load such file -- rack/showexceptions (LoadError)
from /Users/gbade/.rvm/rubies/ruby-2.4.1/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:133:in `rescue in require'
from /Users/gbade/.rvm/rubies/ruby-2.4.1/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:40:in `require'
from /Users/gbade/.rvm/gems/ruby-2.4.1/gems/sinatra-1.0/lib/sinatra/showexceptions.rb:1:in `<top (required)>'
from /Users/gbade/.rvm/rubies/ruby-2.4.1/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from /Users/gbade/.rvm/rubies/ruby-2.4.1/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from /Users/gbade/.rvm/gems/ruby-2.4.1/gems/sinatra-1.0/lib/sinatra/base.rb:6:in `<top (required)>'
from /Users/gbade/.rvm/rubies/ruby-2.4.1/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:68:in `require'
from /Users/gbade/.rvm/rubies/ruby-2.4.1/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:68:in `require'
from /Users/gbade/.rvm/gems/ruby-2.4.1/gems/taps-0.3.24/lib/taps/server.rb:1:in `<top (required)>'
from /Users/gbade/.rvm/rubies/ruby-2.4.1/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:68:in `require'
from /Users/gbade/.rvm/rubies/ruby-2.4.1/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:68:in `require'
from /Users/gbade/.rvm/gems/ruby-2.4.1/gems/taps-0.3.24/lib/taps/cli.rb:61:in `server'
from /Users/gbade/.rvm/gems/ruby-2.4.1/gems/taps-0.3.24/lib/taps/cli.rb:27:in `run'
from /Users/gbade/.rvm/gems/ruby-2.4.1/gems/taps-0.3.24/bin/taps:6:in `<top (required)>'
from /Users/gbade/.rvm/gems/ruby-2.4.1/bin/taps:23:in `load'
from /Users/gbade/.rvm/gems/ruby-2.4.1/bin/taps:23:in `<main>'
from /Users/gbade/.rvm/gems/ruby-2.4.1/bin/ruby_executable_hooks:15:in `eval'
from /Users/gbade/.rvm/gems/ruby-2.4.1/bin/ruby_executable_hooks:15:in `<main>'