Index: build.py
===================================================================
--- a/build.py
+++ b/build.py
@@ -3,5 +3,13 @@
 
 import os, sys, subprocess
 
+DEPENDENCY_SCRIPT = os.path.join(os.path.dirname(__file__), "ensure_dependencies.py")
+
+try:
+  subprocess.check_call([sys.executable, DEPENDENCY_SCRIPT])
+except subprocess.CalledProcessError as e:
+  print >>sys.stderr, e
+  print >>sys.stderr, "Failed to ensure dependencies being up-to-date!"
+
 import buildtools.build
 buildtools.build.processArgs('.', sys.argv)