I am trying to use `beautifulsoup` compatible `lxml` and it is giving me an error:

```
from lxml.html.soupparser import fromstring
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Library/Python/2.7/site-packages/lxml/html/soupparser.py", line 7, in <module>
    from BeautifulSoup import \
ImportError: No module named BeautifulSoup

```

I have `bs4` installed. How do I fix this issue?