Given following log snippets, their explanation, and nothing else, explain what failure, if any, occurred during build of this package.

  Snippets are in a format of [X] : [Y], where [X] is a log snippet, and [Y] is the explanation.

  Snippets are delimited with '================'.

  Drawing on information from all snippets, provide a concise explanation of the issue and recommend a solution.

  Explanation of the issue, and recommended solution, should take a handful of sentences.

  Snippets:

  [error generating index.html: No such file or directory @ rb_sysopen - /usr/share/gems/gems/rdoc-6.8.0/lib/rdoc/generator/template/darkfish/_sidebar_toggle.rhtml (RDoc::Error)
]: [The core issue seems to be a missing file: /usr/share/gems/gems/rdoc-6.8.0/lib/rdoc/generator/template/darkfish/_sidebar_toggle.rhtml. This file is a template used by RDoc to generate the sidebar toggle element in the documentation.]

Issue: The error message you've provided indicates a problem with the RDoc gem, a tool used for generating documentation for Ruby projects. Specifically, it's failing to generate the index.html file, which is a crucial part of the documentation.
Resolution: Check for RDoc Bugs: Search online forums or issue trackers for similar problems and potential solutions.

Check if sources contain that file and try to track it down.