Cookie._CookiePattern is the regular expression used to
retrieve cookies from the HTTP_COOKIE environment
variable.  This pattern assumes that all cookies are in
"name=value" format.  A cookie that doesn't have an
"=value" component is silently skipped over.  (It's
easy to generate a cookie like that - in JavaScript,
document.cookie="broken" is all it takes.)

>>> import Cookie
>>> q = Cookie.SimpleCookie("pie=good; broken;
other=thing")
>>> q
<SimpleCookie: other='thing' pie='good'>

If ignoring cookies without a "=value" component is
intended behaviour, it'd be nice to have a code comment
warning that's what happens.  If it's a bug, the cookie
should be set with an empty value.