Remove excessive escaping of backslashes with usage of raw strings. This
makes it more obvious what is the test input and expected output.
One test is currently failing after editing and was marked as expected
failure.
This commit updates all tests to enforce the Python3 executable. This is
necessary because the `assertRegex` function we use was renamed to this
name only in Python 3.2 [1]
For reference:
s;/usr/bin/env python;/usr/bin/env python3;g
[1]: https://docs.python.org/3/library/unittest.html#unittest.TestCase.assertRegex
The test was failing because it expected "Created task 1"
but it saw "Created task 0a436fd8-7f06-4168-a66d-bbc940498af9".
Instead, the new code looks at the description of task 1.
