I'm just getting familiar with this package, but while browsing through the constants, I noticed this inconsistency:

https://github.com/onelogin/python-saml/blob/3814b0fe98d6ab78cf92b39c15e1785b1cab22bb/src/onelogin/saml2/constants.py#L106

Note the / in the value http://www.w3.org/2000/09/xmld/sig#dsa-sha1, which differs from every spec I can find, including information on the package's README. I imagine this should be http://www.w3.org/2000/09/xmldsig#dsa-sha1.