After F26 brought an update to Ansible 2.4, I can no longer run my ansible playbook. I have a non-standard SSH configuration file, produced by https://docs.openstack.org/tripleo-quickstart. It looks like https://gist.github.com/dtantsur/7ccf5f11aafa2f9e66803be62572874c. I have always invoked it with something like:

    ansible-playbook configure.yml -i undercloud, --ssh-common-args "-F /home/dtantsur/.quickstart/ssh.config.ansible"

(note that host undercloud is defined in the file and is actually a VM on another host).

Until recently my playbook was run correctly. Now it fails when accessing the host:

$ ansible-playbook configure.yml -i undercloud, --ssh-common-args "-F /home/dtantsur/.quickstart/ssh.config.ansible" -vvvv                                                                  master
ansible-playbook 2.4.0.0
  config file = /etc/ansible/ansible.cfg
  configured module search path = [u'/home/dtantsur/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python2.7/site-packages/ansible
  executable location = /usr/bin/ansible-playbook
  python version = 2.7.13 (default, Sep  5 2017, 08:53:59) [GCC 7.1.1 20170622 (Red Hat 7.1.1-3)]
Using /etc/ansible/ansible.cfg as config file
setting up inventory plugins
Parsed undercloud, inventory source with host_list plugin
[DEPRECATION WARNING]: The use of 'include' for tasks has been deprecated. Use 'import_tasks' for static inclusions or 'include_tasks' for dynamic inclusions. This feature will be removed in a future release. 
Deprecation warnings can be disabled by setting deprecation_warnings=False in ansible.cfg.
[DEPRECATION WARNING]: include is kept for backwards compatibility but usage is discouraged. The module documentation details page may explain more about this rationale.. This feature will be removed in a 
future release. Deprecation warnings can be disabled by setting deprecation_warnings=False in ansible.cfg.
statically imported: /home/dtantsur/Projects/config/tasks/repos.yml
statically imported: /home/dtantsur/Projects/config/tasks/vim.yml
statically imported: /home/dtantsur/Projects/config/tasks/devstack.yml
Loading callback plugin default of type stdout, v2.0 from /usr/lib/python2.7/site-packages/ansible/plugins/callback/__init__.pyc

PLAYBOOK: configure.yml *******************************************************************************************************************************************************************************************
1 plays in configure.yml

PLAY [all] ********************************************************************************************************************************************************************************************************

TASK [Gathering Facts] ********************************************************************************************************************************************************************************************
Using module file /usr/lib/python2.7/site-packages/ansible/modules/system/setup.py
<undercloud> ESTABLISH SSH CONNECTION FOR USER: None
<undercloud> SSH: EXEC ssh -vvv -C -o ControlMaster=auto -o ControlPersist=60s -o KbdInteractiveAuthentication=no -o PreferredAuthentications=gssapi-with-mic,gssapi-keyex,hostbased,publickey -o PasswordAuthentication=no -o ConnectTimeout=10 -o ControlPath=/home/dtantsur/.ansible/cp/6ac0e091f5 undercloud '/bin/sh -c '"'"'echo ~ && sleep 0'"'"''
<undercloud> (255, '', 'OpenSSH_7.5p1, OpenSSL 1.1.0f-fips  25 May 2017\r\ndebug1: Reading configuration data /home/dtantsur/.ssh/config\r\ndebug1: Reading configuration data /etc/ssh/ssh_config\r\ndebug3: /etc/ssh/ssh_config line 56: Including file /etc/ssh/ssh_config.d/05-redhat.conf depth 0\r\ndebug1: Reading configuration data /etc/ssh/ssh_config.d/05-redhat.conf\r\ndebug3: /etc/ssh/ssh_config.d/05-redhat.conf line 2: Including file /etc/crypto-policies/back-ends/openssh.config depth 1\r\ndebug1: Reading configuration data /etc/crypto-policies/back-ends/openssh.config\r\ndebug3: gss kex names ok: [gss-gex-sha1-,gss-group14-sha1-]\r\ndebug3: kex names ok: [curve25519-sha256,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1]\r\ndebug1: /etc/ssh/ssh_config.d/05-redhat.conf line 8: Applying options for *\r\ndebug1: auto-mux: Trying existing master\r\ndebug1: Control socket "/home/dtantsur/.ansible/cp/6ac0e091f5" does not exist\r\ndebug2: resolving "undercloud" port 22\r\nssh: Could not resolve hostname undercloud: Name or service not known\r\n')
fatal: [undercloud]: UNREACHABLE! => {
    "changed": false, 
    "msg": "Failed to connect to the host via ssh: OpenSSH_7.5p1, OpenSSL 1.1.0f-fips  25 May 2017\r\ndebug1: Reading configuration data /home/dtantsur/.ssh/config\r\ndebug1: Reading configuration data /etc/ssh/ssh_config\r\ndebug3: /etc/ssh/ssh_config line 56: Including file /etc/ssh/ssh_config.d/05-redhat.conf depth 0\r\ndebug1: Reading configuration data /etc/ssh/ssh_config.d/05-redhat.conf\r\ndebug3: /etc/ssh/ssh_config.d/05-redhat.conf line 2: Including file /etc/crypto-policies/back-ends/openssh.config depth 1\r\ndebug1: Reading configuration data /etc/crypto-policies/back-ends/openssh.config\r\ndebug3: gss kex names ok: [gss-gex-sha1-,gss-group14-sha1-]\r\ndebug3: kex names ok: [curve25519-sha256,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1]\r\ndebug1: /etc/ssh/ssh_config.d/05-redhat.conf line 8: Applying options for *\r\ndebug1: auto-mux: Trying existing master\r\ndebug1: Control socket \"/home/dtantsur/.ansible/cp/6ac0e091f5\" does not exist\r\ndebug2: resolving \"undercloud\" port 22\r\nssh: Could not resolve hostname undercloud: Name or service not known\r\n", 
    "unreachable": true
}
	to retry, use: --limit @/home/dtantsur/Projects/config/configure.retry

PLAY RECAP ********************************************************************************************************************************************************************************************************
undercloud                 : ok=0    changed=0    unreachable=1    failed=0   

As you see, the additional arguments are not present. The issue cannot be reproduced on master, so I assume it was fixed.