Use python3 in tests Some upstream tests call the python interpreter in a subprocess, e.g. to test the custom `process` module or to run simple in-toto step or inspection commands. In debian, where we only build for python3, "python" is not available during build and thus makes those tests fail. This patch replaces "python" with "python3" where applicable.
Use python3 in test fixture Update an inspection in an in-toto layout (base64 encoded), to specify python3 instead of python as run command. ===================================================================
