I am using syncevolution 1.5.
syncevo-http-server line 362 looks like this on my Fedora 22 installation:

page = twisted.web.error.NoResource(message="The session %s was not found" %
sessionid)

But since twisted release 9.0 this is deprecated and since 2 years this feature
is removed. Because of this, the syncevo-http-server has to be fixed. Line 362
changes to

page = twisted.web.resource.NoResource(message="The session %s was not found" %
sessionid)

and line 27 changes from

import twisted.web.error

to

import twisted.web.resource