Updating from 5.6 to 5.7

I followed the intructions, but the update did not succeed,
Steps I followed:
subscription-manager repos --disable=cf-me-5.6-for-rhel-7-rpms
subscription-manager repos --enable=cf-me-5.7-for-rhel-7-rpms
yum clean all
yum update
During the yum update I got a lot of messages like:
Ignoring bcrypt-3.1.10 because its extensions are not built. Try: gem pristine bcrypt --version 3.1.10
Ignoring escape_utils-1.1.0 because its extensions are not built. Try: gem pristine escape_utils --version 1.1.0
Ignoring eventmachine-1.0.7 because its extensions are not built. Try: gem pristine eventmachine --version 1.0.7
Ignoring ffi-1.9.8 because its extensions are not built. Try: gem pristine ffi --version 1.9.8
Ignoring hamlit-2.0.2 because its extensions are not built. Try: gem pristine hamlit --version 2.0.2
Ignoring http_parser.rb-0.6.0 because its extensions are not built. Try: gem pristine http_parser.rb --version 0.6.0
Ignoring json-1.8.2 because its extensions are not built. Try: gem pristine json --version 1.8.2
Ignoring linux_block_device-0.1.0 because its extensions are not built. Try: gem pristine linux_block_device --version 0.1.0
Ignoring memory_buffer-0.1.0 because its extensions are not built. Try: gem pristine memory_buffer --version 0.1.0
Ignoring net_app_manageability-0.1.0 because its extensions are not built. Try: gem pristine net_app_manageability --version 0.1.0
Ignoring nio4r-1.2.1 because its extensions are not built. Try: gem pristine nio4r --version 1.2.1
Ignoring nokogiri-1.6.6.2 because its extensions are not built. Try: gem pristine nokogiri --version 1.6.6.2
Yum update went fine, but cf-me does not want to start.
When executing rake EVM command I got the message:

rake db:migrate
Could not find nokogiri-1.6.8 in any of the sources
Run

bundle install

The nokogiri-1.6.8 is installed on the system.
In the documentation no further steps are mentioned to resolve this.