Use pre-packaged Python libraries instead of /usr

Change-Id: If27064f17c243ab1b0c98957a013eb86a37b5cb0
diff --git a/third_party/matplotlib-cpp/BUILD b/third_party/matplotlib-cpp/BUILD
index 8eb8734..3d3959c 100644
--- a/third_party/matplotlib-cpp/BUILD
+++ b/third_party/matplotlib-cpp/BUILD
@@ -6,7 +6,7 @@
         "matplotlibcpp.h"
     ],
     deps = [
-        "@usr_repo//:python2.7_lib",
+        "@python_repo//:python2.7_lib",
     ],
     visibility = ["//visibility:public"],
     restricted_to = ["//tools:k8"],