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:

  [WARNING: The found license expression 'DolphinDB' is not a valid SPDX expression. Inspect the project manually to find the license]: [This is a warning about license format. While it is important that all packages follow certain conventions, this is not the cause of failed build.]
=============
[Fatal exception occurred: sdist not found.]: [This exception is reason for the build failure. Without sdist, the source tarball, there is nothing to build and therefore nothing to package.]
=============
[stderr: 

Unable to generate spec for `dolphindb']: [Final error, stating that there was no way to generate spec for the package.]

Issue: The source tarball, sdist, was not present during build.
Resolution: Ensure presence of sources before build commences.