Provide Python 3 matplotlib

Once I get around to making numpy/scipy imported for Python 3, I'll
probably upgrade everything to Python 3 and drop Python 2 support from
the codebase, but I don't feel like doing that quite yet.

Change-Id: I164c8fbb3ce922a83b56e46f5cc432004c3a989c
diff --git a/y2017/control_loops/python/BUILD b/y2017/control_loops/python/BUILD
index 50f5584..6afb242 100644
--- a/y2017/control_loops/python/BUILD
+++ b/y2017/control_loops/python/BUILD
@@ -58,7 +58,7 @@
         "//external:python-gflags",
         "//external:python-glog",
         "//frc971/control_loops/python:controls",
-        "@matplotlib",
+        "@matplotlib_repo//:matplotlib2.7",
     ],
 )
 
@@ -106,7 +106,7 @@
         "//external:python-gflags",
         "//external:python-glog",
         "//frc971/control_loops/python:controls",
-        "@matplotlib",
+        "@matplotlib_repo//:matplotlib2.7",
     ],
 )
 
@@ -123,7 +123,7 @@
         "//external:python-gflags",
         "//external:python-glog",
         "//frc971/control_loops/python:controls",
-        "@matplotlib",
+        "@matplotlib_repo//:matplotlib2.7",
     ],
 )
 
@@ -168,7 +168,7 @@
         "//external:python-gflags",
         "//external:python-glog",
         "//frc971/control_loops/python:controls",
-        "@matplotlib",
+        "@matplotlib_repo//:matplotlib2.7",
     ],
 )