Upgrade webassets to v2.0

[m4rk3r]

Description

Upgrade webassets dependency to use version 2.0

Motivation and Context

Version 2.0 updates usage of yaml to use safe_load instead of load which was deprecated and now throws an error when a loader isn't also supplied:

Traceback (most recent call last):
  File "/code/./webrecorder/main.py", line 9, in <module>
    application = MainController().app
  File "/code/./webrecorder/maincontroller.py", line 110, in __init__
    jinja_env = self.init_jinja_env(config)
  File "/code/./webrecorder/maincontroller.py", line 200, in init_jinja_env
    jinja_env_wrapper = JinjaEnv(assets_path=assets_path,
  File "/usr/local/lib/python3.8/site-packages/pywb-2.6.7-py3.8.egg/pywb/rewrite/templateview.py", line 98, in __init__
    assets_env = assets_loader.load_environment()
  File "/usr/local/lib/python3.8/site-packages/webassets/loaders.py", line 201, in load_environment
    obj = self.yaml.load(f) or {}
TypeError: load() missing 1 required positional argument: 'Loader'

Screenshots (if appropriate):

Types of changes

• Replay fix (fixes a replay specific issue)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added or updated tests to cover my changes.
• All new and existing tests passed.