Don't implicitly run "pub get".

test/run/nonexistent_script_test.dart

Index: test/run/nonexistent_script_test.dart
diff --git a/test/run/nonexistent_script_test.dart b/test/run/nonexistent_script_test.dart
index 12348914b2cb86805d31397df88293dffc7f0a2a..060447f37e23cc3e029b1900e4b4f342ad32c832 100644
--- a/test/run/nonexistent_script_test.dart
+++ b/test/run/nonexistent_script_test.dart
@@ -14,6 +14,7 @@ main() {
       d.appPubspec()
     ]).create();
 
+    pubGet();
     var pub = pubRun(args: [p.join("bin", "script")]);
     pub.stderr.expect("Could not find ${p.join("bin", "script.dart")}.");
     pub.shouldExit(exit_codes.NO_INPUT);