Copy all requirements of slapos.libnetworkcache.

This allows complex library usage in bootstrap process.

src/zc/buildout/buildout.py

@@ -438,7 +438,12 @@ class Buildout(UserDict.DictMixin):
         entries = []
         copy_list = ['setuptools', 'zc.buildout']
         if LIBNETWORKCACHE_ENABLED:
-          copy_list.append('slapos.libnetworkcache')
+            copy_list.append('slapos.libnetworkcache')
+            networkcache_dist = ws.find(pkg_resources.Requirement.parse(
+                'slapos.libnetworkcache'))
+            for requirement in [q.key for q in networkcache_dist.requires()]:
+                if requirement not in copy_list:
+                    copy_list.append(requirement)
         for name in copy_list:
             r = pkg_resources.Requirement.parse(name)
             dist = ws.find(r)