==> Building py-mpmath [PythonPackage] ==> Executing phase : 'build' ==> Error: TypeError: 'str' object is not callable /Users/davydden/spack/lib/spack/spack/build ...

This appears to be caused by a syntax issue in the exception raising line. The string is not properly formatted or completed, and Python interprets it as a function call, which results in a 'str' ...