Make matplotlib targets depend on gtk

Otherwise matplotlib complains it has no graphical backend and won't pop
up a plot.

Change-Id: I73b024c957ea87d1f440f1b73f0806440655c0fd
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
diff --git a/frc971/control_loops/python/BUILD b/frc971/control_loops/python/BUILD
index 7b46439..c547833 100644
--- a/frc971/control_loops/python/BUILD
+++ b/frc971/control_loops/python/BUILD
@@ -29,6 +29,7 @@
         "//frc971/control_loops/python:controls",
         "@pip//glog",
         "@pip//matplotlib",
+        "@pip//pygobject",
         "@pip//python_gflags",
     ],
 )
@@ -77,6 +78,7 @@
         ":controls",
         ":python_init",
         "@pip//matplotlib",
+        "@pip//pygobject",
     ],
 )
 
@@ -90,6 +92,7 @@
         ":controls",
         ":python_init",
         "@pip//matplotlib",
+        "@pip//pygobject",
     ],
 )
 
@@ -132,6 +135,7 @@
         ":python_init",
         "@pip//glog",
         "@pip//matplotlib",
+        "@pip//pygobject",
     ],
 )
 
@@ -153,6 +157,7 @@
         "//aos/util:py_trapezoid_profile",
         "//frc971/control_loops:python_init",
         "@pip//matplotlib",
+        "@pip//pygobject",
     ],
 )
 
@@ -166,6 +171,7 @@
         "//aos/util:py_trapezoid_profile",
         "//frc971/control_loops:python_init",
         "@pip//matplotlib",
+        "@pip//pygobject",
     ],
 )