Update default API version to v1.39 (#2512)

* Update default API version to v1.39

When running the docker-py integration tests in the Moby repository, some
tests were skipped because the API version used was too low:

    SKIPPED [1] tests/integration/api_service_test.py:882: API version is too low (< 1.38)
    SKIPPED [1] tests/integration/api_swarm_test.py:59: API version is too low (< 1.39)
    SKIPPED [1] tests/integration/api_swarm_test.py:38: API version is too low (< 1.39)
    SKIPPED [1] tests/integration/api_swarm_test.py:45: API version is too low (< 1.39)
    SKIPPED [1] tests/integration/api_swarm_test.py:52: API version is too low (< 1.39)

While it's possible to override the API version to use for testing
using the `DOCKER_TEST_API_VERSION` environment variable, we may want
to set the default to a version that supports all features that were
added.

This patch updates the default API version to v1.39, which is the minimum
version required for those features, and corresponds with Docker 18.09.

Note that the API version of the current (19.03) Docker release is v1.40,
but using that version as default would exclude users that did not update
their Docker version yet (and would not be needed yet for the features provided).

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

* Makefile: set DOCKER_TEST_API_VERSION to v1.39

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

Author: thaJeztah

Makefile

@@ -41,7 +41,7 @@ integration-test: build
 integration-test-py3: build-py3
 	docker run -t --rm -v /var/run/docker.sock:/var/run/docker.sock docker-sdk-python3 py.test -v tests/integration/${file}
 
-TEST_API_VERSION ?= 1.35
+TEST_API_VERSION ?= 1.39
 TEST_ENGINE_VERSION ?= 19.03.12
 
 .PHONY: setup-network

docker/constants.py

@@ -1,7 +1,7 @@
 import sys
 from .version import version
 
-DEFAULT_DOCKER_API_VERSION = '1.35'
+DEFAULT_DOCKER_API_VERSION = '1.39'
 MINIMUM_DOCKER_API_VERSION = '1.21'
 DEFAULT_TIMEOUT_SECONDS = 60
 STREAM_HEADER_SIZE_BYTES = 8