[pkg] Use Twisted < 16.0.0
We have some test failures with 16.0.0, such as:
- test_put_content (unittest_server.ETwistHTTPTC)
- test_base_url (unittest_httptest.TwistedCWAnonTC)
(grafted from 10c12f31d0fe38c2e8814176fc42bf2ea210efdf)
[MESSAGES CONTROL]
disable-msg = C0301
[VARIABLES]
# Enable / disable this checker
enable-variables = yes
additional-builtins = _, display_name
[BASIC]
required-attributes=
attr-rgx = (w|[a-z_][a-z0-9_]{2,30})
variable-rgx = (w|[a-z_][a-z0-9_]{2,30})$
argument-rgx = (w|[a-z_][a-z0-9_]{2,30})$
[TYPECHECK]
generated-members=debug,info,notice,warning,error,critical,exception