with facundo we were tracking this bug down. mhammond is right about 
that read() should allow 0 size responses, but the bug is that the 
response is "not closed". HTTPResponse.read() says:

        if amt is None:
            # unbounded read
            if self.length is None:
                s = self.fp.read()
            else:
                s = self._safe_read(self.length)
                self.length = 0
            self.close()        # we read everything
            return s

see that if self.close()s, which really closes the fp created with 
makefile() in the constructor. this does not closes the underlying 
socket, as you can see trying this short example:

import httplib

c= httplib.HTTPConnection ('www.python.org', 80)

c.request ('GET', '/index.html')
a1= c.getresponse ()
data1= a1.read()

c.request ('GET', '/404.html')
a2= c.getresponse ()
data2= a2.read()

and run it under strace -e network,file.

if the last part of read is changed to this, read(n) works just like 
read() does:

        # we do not use _safe_read() here because this may be 
a .will_close
        # connection, and the user is reading more bytes than will be 
provided
        # (for example, reading in 1k chunks)
        s = self.fp.read(amt)
        if self.length is not None:
            self.length -= len(s)
        if len(s)==0:
            self.close ()

        return s