Docker SDK for Python 7+: make sure that ssl_version is not passed, and error out if it was explicitly set (#715)

* Do not accept ssl_version for Docker SDK for Python 7.0.0+.

* Add changelog fragment.

* Generally avoid sending None values to TLSConfig. Potentially prevents similar errors in the future, assuming the users do not pass values in.

* Python 2.6 compatibility.

changelogs/fragments/715-docker-7.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - "modules and plugins using the Docker SDK for Python - remove ``ssl_version`` from the parameters passed to Docker SDK for Python 7.0.0+. Explicitly fail with a nicer error message if it was explicitly set in this case (https://github.com/ansible-collections/community.docker/pull/715)."

plugins/doc_fragments/docker.py

@@ -72,6 +72,8 @@ options:
             - Provide a valid SSL version number. Default value determined by L(SSL Python module, https://docs.python.org/3/library/ssl.html).
             - If the value is not specified in the task, the value of environment variable E(DOCKER_SSL_VERSION) will be
               used instead.
+            - B(Note:) this option is no longer supported for Docker SDK for Python 7.0.0+. Specifying it with Docker SDK for
+              Python 7.0.0 or newer will lead to an error.
         type: str
     tls:
         description:

plugins/module_utils/common.py

@@ -122,6 +122,20 @@ if not HAS_DOCKER_PY:
 
 
 def _get_tls_config(fail_function, **kwargs):
+    if 'ssl_version' in kwargs and LooseVersion(docker_version) >= LooseVersion('7.0.0b1'):
+        ssl_version = kwargs.pop('ssl_version')
+        if ssl_version is not None:
+            fail_function(
+                "ssl_version is not compatible with Docker SDK for Python 7.0.0+. You are using"
+                " Docker SDK for Python {docker_py_version}. The ssl_version option (value: {ssl_version})"
+                " has either been set directly or with the environment variable DOCKER_SSL_VERSION."
+                " Make sure it is not set, or switch to an older version of Docker SDK for Python.".format(
+                    docker_py_version=docker_version,
+                    ssl_version=ssl_version,
+                )
+            )
+    # Filter out all None parameters
+    kwargs = dict((k, v) for k, v in kwargs.items() if v is not None)
     try:
         tls_config = TLSConfig(**kwargs)
         return tls_config