old_contents: from spack import *
  
  class TheSilverSearcher(Package):
      """Fast recursive grep alternative"""
      homepage = "http://geoff.greer.fm/ag/"
      url      = "http://geoff.greer.fm/ag/releases/the_silver_searcher-0.30.0.tar.gz"
  
      version('0.30.0', '95e2e7859fab1156c835aff7413481db')
  
      depends_on('pcre')
      depends_on('xz')
  
      def install(self, spec, prefix):
          configure("--prefix=%s" % prefix)
  
          make()
          make("install")
  
new_contents: from spack import *
  
  class TheSilverSearcher(Package):
      """Fast recursive grep alternative"""
      homepage = "http://geoff.greer.fm/ag/"
      url      = "http://geoff.greer.fm/ag/releases/the_silver_searcher-0.30.0.tar.gz"
  
      version('0.30.0', '95e2e7859fab1156c835aff7413481db')
  
      depends_on('pcre')
      depends_on('xz')
      depends_on('pkg-config')
  
      def install(self, spec, prefix):
          configure("--prefix=%s" % prefix)
  
          make()
          make("install")
  
subject: add missing dependency