dist: move "import pip" from module level to download_wheels

The aim of this is that pip is no longer a dependency to be able to run test_imports.

direct/src/dist/commands.py

@@ -8,7 +8,6 @@ from __future__ import print_function
 
 import collections
 import os
-import pip
 import plistlib
 import sys
 import subprocess
@@ -396,6 +395,8 @@ class build_apps(setuptools.Command):
         directory containing the Python runtime libraries, which will be added
         to sys.path."""
 
+        import pip
+
         self.announce('Gathering wheels for platform: {}'.format(platform), distutils.log.INFO)
 
         whldir = os.path.join(self.build_base, '__whl_cache__')