Task LSMR-8: attempt to switch to Python 3

CMake/FindPython3Module.cmake

@@ -77,7 +77,7 @@ function(find_python3_module _module)
       set(ENV{PYTHONPATH} ${PYTHON_${_MODULE}_FIND_HINTS}:$ENV{PYTHONPATH})
       set(_cmd "from __future__ import print_function; import ${_module}; print(${_module}.__file__)")
       execute_process(
-        COMMAND "$/usr/bin/python3" "-c" "${_cmd}"
+        COMMAND "/usr/bin/python3" "-c" "${_cmd}"
         RESULT_VARIABLE _result
         OUTPUT_VARIABLE _output
         ERROR_QUIET