Review package compatibility

Nobody has claimed this yet.

Netlify informs me that a recent build is failing: ([full log in Gist](https://gist.github.com/uranusjr/00dc3ead34d373f49cd6b920d33beae0))

```
3:03:39 PM: Traceback (most recent call last):
3:03:39 PM: File "/opt/buildhome/python2.7/bin/invoke", line 10, in
3:03:39 PM: sys.exit(program.run())
3:03:39 PM: File "/opt/buildhome/python2.7/local/lib/python2.7/site-packages/invoke/program.py", line 384, in run
3:03:39 PM: self.execute()
3:03:39 PM: File "/opt/buildhome/python2.7/local/lib/python2.7/site-packages/invoke/program.py", line 566, in execute
3:03:39 PM: executor.execute(*self.tasks)
3:03:39 PM: File "/opt/buildhome/python2.7/local/lib/python2.7/site-packages/invoke/executor.py", line 129, in execute
3:03:39 PM: result = call.task(*args, **call.kwargs)
3:03:39 PM: File "/opt/buildhome/python2.7/local/lib/python2.7/site-packages/invoke/tasks.py", line 127, in __call__
3:03:39 PM: result = self.body(*args, **kwargs)
3:03:39 PM: File "/opt/build/repo/tasks.py", line 119, in build
3:03:39 PM: lektor_cli_ctx.load_plugins()
3:03:39 PM: File "/opt/buildhome/python2.7/local/lib/python2.7/site-packages/lektor/cli.py", line 131, in load_plugins
3:03:39 PM: initialize_plugins(self.get_env())
3:03:39 PM: File "/opt/buildhome/python2.7/local/lib/python2.7/site-packages/lektor/pluginsystem.py", line 122, in initialize_plugins
3:03:39 PM: plugins = load_plugins()
3:03:39 PM: File "/opt/buildhome/python2.7/local/lib/python2.7/site-packages/lektor/pluginsystem.py", line 116, in load_plugins
3:03:39 PM: rv[ep.name] = ep.load()
3:03:39 PM: File "/opt/buildhome/python2.7/local/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2434, in load
3:03:39 PM: return self.resolve()
3:03:39 PM: File "/opt/buildhome/python2.7/local/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2440, in resolve
3:03:39 PM: module = __import__(self.module_name, fromlist=['__name__'], level=0)
3:03:39 PM: File "/opt/build/repo/packages/lektor-atom/lektor_atom.py", line 22, in
3:03:39 PM: from werkzeug.contrib.atom import AtomFeed
3:03:39 PM: ImportError: No module named contrib.atom
```

Not sure what the problem is atm.

Start with the Netlify traceback and inspect packages/lektor-atom/lektor_atom.py, especially the import of werkzeug.contrib.atom. Review the build entry point in tasks.py and the package versions used by the Netlify environment. Done means the site build completes without the ImportError and the compatibility fix is reproducible.

Written by the indexing model from the issue text.