Compat with pip10+

This fixes docker#2001

setup.py

@@ -5,13 +5,17 @@
 import os
 import sys
 
-import pip
+
+try:
+ from pip import get_installed_distributions
+except ImportError:
+ from pip._internal import get_installed_distributions
 
 from setuptools import setup, find_packages
 
 try:
  if 'docker-py' in [
- x.project_name for x in pip.get_installed_distributions()]:
+ x.project_name for x in get_installed_distributions()]:
  print(
  'ERROR: "docker-py" needs to be uninstalled before installing this'
  ' package:\npip uninstall docker-py', file=sys.stderr