This MR fixes cosmetic issues encountered in CI (mostly harmless, but producing ugly output) after the default algorithm randomization changes merged recently.
echo_icould've been previously used while undefined when calling
testcrypto.shdirectly (e.g. job#2865727)
PYTHONinterpreter could've been undefined at certain stages of the test preparations, which would result in an error message on some platforms (e.g. job#2866331)
This MR also introduces an explicit check for Python interpreter before running system tests.
Closes #3747 (closed)
Related #3503 (closed)