I'm attempting to launch a local html file from python in the default browser (right now my default is Google Chrome if I double-click on a .html file, Chrome launches.)

When I use python's `webbrowser.open()`, IE launches instead, with a blank address bar.

```
Python 2.7.1 (r271:86832, Nov 27 2010, 17:19:03) [MSC v.1500 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import webbrowser
>>> filename = 'test.html'
>>> webbrowser.open('file://'+filename)
True
>>> print(webbrowser.get().__class__.__name__)
WindowsDefault

```

I've checked my default programs and they look correct. I'm on Win 7 SP1. Why is Chrome not launching?

**Update**: The code will be running on unknown OS's and machines, so hardcoding or registering browsers or path updates are not options. I'm thinking that parsing the url for `file://` and then doing an `os.path.exists` check and `os.path.realpath` might be the answer.