Tests wrongly return empty stdout depending on the format of test_script [QA664]

[firebird-automations]

Submitted by: @asfernandes

I have problem with many tests, that returns empty stdout.

For example:

======================================================================
FAIL: bugs.core_1171
----------------------------------------------------------------------
Expected standard output from ISQL does not match actual output.

----------------------------------------------------------------------
Ran 1 tests in 0.494s

FAILED (fails=1)

ISQL_stdout_actual is empty.

To make it work, I need to change test from:

'test_script': "select cast ('-2.488355210669293e+39' as double
precision) from rdb$database;",

to:

'test_script':
"""
select cast ('-2.488355210669293e+39' as double precision) from
rdb$database;
""",

Test is run in a docker container with Ubuntu Bionic, connected to Firebird in the host also with Ubuntu Bionic.