docker-compose: backport upstream patch for pyyaml 4.x support

Otherwise docker-compose fails at runtime with:

docker-compose
Traceback (most recent call last):
  File "/usr/bin/docker-compose", line 6, in <module>
    from pkg_resources import load_entry_point
  File "usr/lib/python2.7/site-packages/pkg_resources/__init__.py", line 3123, in <module>
  File "usr/lib/python2.7/site-packages/pkg_resources/__init__.py", line 3107, in _call_aside
  File "usr/lib/python2.7/site-packages/pkg_resources/__init__.py", line 3136, in _initialize_master_working_set
  File "usr/lib/python2.7/site-packages/pkg_resources/__init__.py", line 580, in _build_master
  File "usr/lib/python2.7/site-packages/pkg_resources/__init__.py", line 593, in _build_from_requirements
  File "usr/lib/python2.7/site-packages/pkg_resources/__init__.py", line 781, in resolve
pkg_resources.DistributionNotFound: The 'PyYAML<4,>=3.10' distribution was not found and is required by docker-compose

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>