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: downloading 'https://github.com/SebWouters/CheMPS2/archive/d8ac508.tar.gz' failed
          status_code: 6
          status_string: "Could not resolve hostname"
          log:
          --- LOG BEGIN ---
          Could not resolve host: github.com]: [This snippet shows why the build failed.]

Issue: Additional upstream source is used during the build and the build failed when trying to download it. The message shows that host name couldn't be resolved.
Resolution: Check the URL of the additional upstream source whether the path to the source is correct. In case it is, check the status of the server and/or retry the build later.