Explicitly convert from bytes to string so that splitting the string is
successful. This change works with python 2 as well.

Closes #4182

They are not executable anymore, and tests are now meant to be run
through pytest.

That line is testing Python's list.count method, instead of yedit.
The assertion right above is a superset of it, as it checks for
equality to some expected value.

if we're given path a.b.c and the existing object is:
a:
  b:
   - item1
raise an exception due to unexpected objects found while traversing the path (ie. b is a list, not a dict)

also, add_entry assumes new dicts for each sub element when creating elements besides the final assignment value.
doing something like a.b.c[0] = 12 where 'c' doesn't exist raises an exception

add test cases to cover:
access path that differs from existing object
create new objects with an embedded list in the path
create new object with a list at the end (define the end list in the passed in 'value' to avoid this exception)

was: separate lib_ unit tests from other unit tests

We were not running those tests in CI, bad :(