[DRE-maint] Bug#1024177: cannot use plugin due to incompatibility?

[VA]

Package: ruby-jekyll-feed
Version: 0.15.1-2

I'm using jekyll with those plugins in `_config.yml`:

plugins:
   - jekyll-sitemap
   - jekyll-feed

I get this error:

   Dependency Error: Yikes! It looks like you don't have jekyll-feed or 
one of its dependencies installed. In order to use Jekyll as currently 
configured, you'll need to install this gem. The full error message from 
Ruby is: 'Unable to activate jekyll-3.9.0, because liquid-5.4.0 
conflicts with liquid (~> 4.0), mercenary-0.4.0 conflicts with mercenary 
(~> 0.3.3)' If you run into trouble, you can find helpful resources at 
https://jekyllrb.com/help/!
jekyll 3.9.0 | Error:  jekyll-feed
/usr/lib/ruby/vendor_ruby/jekyll/external.rb:68:in `rescue in block in 
require_with_graceful_fail': jekyll-feed 
(Jekyll::Errors::MissingDependencyException)
	from /usr/lib/ruby/vendor_ruby/jekyll/external.rb:56:in `block in 
require_with_graceful_fail'
	from /usr/lib/ruby/vendor_ruby/jekyll/external.rb:55:in `each'
[snip backtrace]
/usr/lib/ruby/vendor_ruby/rubygems/specification.rb:2248:in 
`raise_if_conflicts': Unable to activate jekyll-3.9.0, because 
liquid-5.4.0 conflicts with liquid (~> 4.0), mercenary-0.4.0 conflicts 
with mercenary (~> 0.3.3) (Gem::ConflictError)
[snip backtrace]
/usr/lib/ruby/vendor_ruby/rubygems/specification.rb:2248:in 
`raise_if_conflicts': Unable to activate jekyll-3.9.0, because 
liquid-5.4.0 conflicts with liquid (~> 4.0), mercenary-0.4.0 conflicts 
with mercenary (~> 0.3.3) (Gem::ConflictError)
[snip backtrace]
<internal:/usr/lib/ruby/vendor_ruby/rubygems/core_ext/kernel_require.rb>:85:in 
`require': cannot load such file -- jekyll-feed (LoadError)
Did you mean?  jekyll
[snip backtrace]

This is what's installed:

jekyll                                   3.9.0+dfsg-5
ruby-jekyll-feed                         0.15.1-2
ruby-jekyll-sass-converter               1.5.2-3
ruby-jekyll-sitemap                      1.4.0-2
ruby-jekyll-watch                        2.2.1-1
ruby-liquid                              5.4.0-2
ruby-mercenary                           0.4.0-1