Fix failing tests

A number of tests failed, because there's check in the LSMTool source code
on the version number of SciPy. This check breaks if the version number is
that of a release candidate. Now, I'm not sure why `python test`
pulls in a pre-release version of SciPy, but it easier to fix this in the
source code.

TODO: the use of `distutils.version` is deprecated; it shoud be replaced
      with `packaging.version`
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