According to Chris Heisel, the author of basecampreporting, the reason why the original basecamp.py is not working properly is the use of base64. When you encode a string with base64, it adds a newline at the end of the encoded string. The newline is what irritates basecamp. Get rid of the newline, and basecamp.py works.

This is how Chris Heisel did it (again around line 64):

def __init__(self, baseURL, username, password):
self.baseURL = baseURL
if self.baseURL[-1] == '/':
self.baseURL = self.baseURL[:-1]

self.opener = urllib2.build_opener()

self.auth_string = '%s:%s' % (username, password)
self.encoded_auth_string = base64.encodestring(self.auth_string)

#Python 2.5, at least on Ubuntu is adding a newline when encoding,
#which Basecamp chokes on and returns an HTTP 400
self.encoded_auth_string = self.encoded_auth_string.replace('n', '')
self.headers = [
('Content-Type', 'application/xml'),
('Accept', 'application/xml'),
('Authorization', 'Basic %s' % self.encoded_auth_string), ]
self.opener.addheaders = self.headers