Fix failing tests in `tests/viewer_test.py`.

[nicomiguelino]

Overview of the Issue

test_empty (viewer_test.TestEmptyPl) ... ERROR

======================================================================
ERROR: test_empty (viewer_test.TestEmptyPl)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/src/app/tests/viewer_test.py", line 49, in test_empty
    self.u.main()
  File "/usr/src/app/viewer.py", line 429, in main
    setup()
  File "/usr/src/app/viewer.py", line 359, in setup
    load_browser()
  File "/usr/src/app/viewer.py", line 257, in load_browser
    browser = sh.Command('ScreenlyWebview')(_bg=True, _err_to_out=True)
  File "/usr/local/lib/python2.7/dist-packages/sh.py", line 508, in __init__
    if not path: raise CommandNotFound(path)
CommandNotFound: None
-------------------- >> begin captured logging << --------------------
root: DEBUG: Starting viewer.py
root: DEBUG: Reading config-file...
root: DEBUG: Reading config-file...
root: INFO: Loading browser...
--------------------- >> end captured logging << ---------------------

----------------------------------------------------------------------
Ran 1 test in 0.831s

FAILED (errors=1)

Reproduction Steps

First Time Setup

docker-compose -f docker-compose.dev.yml build
docker-compose -f docker-compose.dev.yml up -d
docker-compose -f docker-compose.dev.yml exec srly-ose-test bash bin/prepare_test_environment.sh -s

Running the Tests

docker-compose -f docker-compose.dev.yml exec srly-ose-test nosetests -v -a 'fixme' tests/viewer_test.py

Environment

• WSL 2 (Ubuntu 22.04, x86, 64-bit)
• Docker Desktop for Windows (accessible via WSL 2)