undefined method `has_content_type?' for nil:NilClass
this looks similar to #458 (closed) but it was seen on a 3.5.3 schleuder installation.
undefined method `has_content_type?' for nil:NilClass
/opt/schleuder/bundler/ruby/2.7.0/gems/mail-gpg-0.4.2/lib/mail/gpg/sign_part.rb:22:in `verify_signature'
/opt/schleuder/bundler/ruby/2.7.0/gems/mail-gpg-0.4.2/lib/mail/gpg/mime_signed_message.rb:9:in `setup'
/opt/schleuder/bundler/ruby/2.7.0/gems/mail-gpg-0.4.2/lib/mail/gpg.rb:144:in `verify'
/opt/schleuder/bundler/ruby/2.7.0/gems/mail-gpg-0.4.2/lib/mail/gpg/message_patch.rb:91:in `verify'
/opt/schleuder/lib/schleuder/mail/message.rb:31:in `setup'
/opt/schleuder/lib/schleuder/runner.rb:38:in `run'
/opt/schleuder/lib/schleuder/cli.rb:36:in `work'
/opt/schleuder/bundler/ruby/2.7.0/gems/thor-0.20.3/lib/thor/command.rb:27:in `run'
/opt/schleuder/bundler/ruby/2.7.0/gems/thor-0.20.3/lib/thor/invocation.rb:126:in `invoke_command'
/opt/schleuder/bundler/ruby/2.7.0/gems/thor-0.20.3/lib/thor.rb:387:in `dispatch'
/opt/schleuder/bundler/ruby/2.7.0/gems/thor-0.20.3/lib/thor/base.rb:466:in `start'
/opt/schleuder/bin/schleuder:13:in `<top (required)>'
/opt/schleuder/bundler/ruby/2.7.0/bin/schleuder:23:in `load'
/opt/schleuder/bundler/ruby/2.7.0/bin/schleuder:23:in `<top (required)>'
/opt/rh/rh-ruby27/root/usr/share/gems/gems/bundler-2.1.4/lib/bundler/cli/exec.rb:63:in `load'
/opt/rh/rh-ruby27/root/usr/share/gems/gems/bundler-2.1.4/lib/bundler/cli/exec.rb:63:in `kernel_load'
/opt/rh/rh-ruby27/root/usr/share/gems/gems/bundler-2.1.4/lib/bundler/cli/exec.rb:28:in `run'
/opt/rh/rh-ruby27/root/usr/share/gems/gems/bundler-2.1.4/lib/bundler/cli.rb:476:in `exec'
/opt/rh/rh-ruby27/root/usr/share/gems/gems/bundler-2.1.4/lib/bundler/vendor/thor/lib/thor/command.rb:27:in `run'
/opt/rh/rh-ruby27/root/usr/share/gems/gems/bundler-2.1.4/lib/bundler/vendor/thor/lib/thor/invocation.rb:127:in `invoke_command'
/opt/rh/rh-ruby27/root/usr/share/gems/gems/bundler-2.1.4/lib/bundler/vendor/thor/lib/thor.rb:399:in `dispatch'
/opt/rh/rh-ruby27/root/usr/share/gems/gems/bundler-2.1.4/lib/bundler/cli.rb:30:in `dispatch'
/opt/rh/rh-ruby27/root/usr/share/gems/gems/bundler-2.1.4/lib/bundler/vendor/thor/lib/thor/base.rb:476:in `start'
/opt/rh/rh-ruby27/root/usr/share/gems/gems/bundler-2.1.4/lib/bundler/cli.rb:24:in `start'
/opt/rh/rh-ruby27/root/usr/share/gems/gems/bundler-2.1.4/libexec/bundle:46:in `block in <top (required)>'
/opt/rh/rh-ruby27/root/usr/share/gems/gems/bundler-2.1.4/lib/bundler/friendly_errors.rb:123:in `with_friendly_errors'
/opt/rh/rh-ruby27/root/usr/share/gems/gems/bundler-2.1.4/libexec/bundle:34:in `<top (required)>'
/opt/rh/rh-ruby27/root/usr/bin/bundle:23:in `load'
/opt/rh/rh-ruby27/root/usr/bin/bundle:23:in `<main>'
Original email is available. Will need to validate it with schleuder 4 and then also whether I can easily reproduce it.