set version to 'auto' to avoid breaking on old engine versions

Signed-off-by: aiordache <[email protected]>

Author: aiordache

docker/api/client.py

@@ -7,6 +7,19 @@
 import six
 import websocket
 
+from .. import auth
+from ..constants import (DEFAULT_DOCKER_API_VERSION, DEFAULT_NUM_POOLS,
+                         DEFAULT_NUM_POOLS_SSH, DEFAULT_TIMEOUT_SECONDS,
+                         DEFAULT_USER_AGENT, IS_WINDOWS_PLATFORM,
+                         MINIMUM_DOCKER_API_VERSION, STREAM_HEADER_SIZE_BYTES)
+from ..errors import (DockerException, InvalidVersion, TLSParameterError,
+                      create_api_error_from_http_exception)
+from ..tls import TLSConfig
+from ..transport import SSLHTTPAdapter, UnixHTTPAdapter
+from ..utils import check_resource, config, update_headers, utils
+from ..utils.json_stream import json_stream
+from ..utils.proxy import ProxyConfig
+from ..utils.socket import consume_socket_output, demux_adaptor, frames_iter
 from .build import BuildApiMixin
 from .config import ConfigApiMixin
 from .container import ContainerApiMixin
@@ -19,22 +32,7 @@
 from .service import ServiceApiMixin
 from .swarm import SwarmApiMixin
 from .volume import VolumeApiMixin
-from .. import auth
-from ..constants import (
-    DEFAULT_TIMEOUT_SECONDS, DEFAULT_USER_AGENT, IS_WINDOWS_PLATFORM,
-    DEFAULT_DOCKER_API_VERSION, MINIMUM_DOCKER_API_VERSION,
-    STREAM_HEADER_SIZE_BYTES, DEFAULT_NUM_POOLS_SSH, DEFAULT_NUM_POOLS
-)
-from ..errors import (
-    DockerException, InvalidVersion, TLSParameterError,
-    create_api_error_from_http_exception
-)
-from ..tls import TLSConfig
-from ..transport import SSLHTTPAdapter, UnixHTTPAdapter
-from ..utils import utils, check_resource, update_headers, config
-from ..utils.socket import frames_iter, consume_socket_output, demux_adaptor
-from ..utils.json_stream import json_stream
-from ..utils.proxy import ProxyConfig
+
 try:
     from ..transport import NpipeHTTPAdapter
 except ImportError:
@@ -183,14 +181,14 @@ def __init__(self, base_url=None, version=None,
             self.base_url = base_url
 
         # version detection needs to be after unix adapter mounting
-        if version is None:
-            self._version = DEFAULT_DOCKER_API_VERSION
-        elif isinstance(version, six.string_types):
-            if version.lower() == 'auto':
-                self._version = self._retrieve_server_version()
-            else:
-                self._version = version
+        if version is None or (
+            isinstance(version, six.string_types) and 
+            version.lower()) == 'auto':
+            self._version = self._retrieve_server_version()
         else:
+            self._version = version
+        
+        if not isinstance(self._version, six.string_types):
             raise DockerException(
                 'Version parameter must be a string or None. Found {0}'.format(
                     type(version).__name__