mach: always call ensure_bootstrapped before call_rustup_run

python/servo/command_base.py

@@ -360,7 +360,7 @@ class CommandBase(object):
 
     def call_rustup_run(self, args, **kwargs):
         if self.config["tools"]["use-rustup"]:
-            self.ensure_rustup_version()
+            assert self.context.bootstrapped
             args = ["rustup" + BIN_SUFFIX, "run", "--install", self.rust_toolchain()] + args
         else:
             args[0] += BIN_SUFFIX

python/servo/testing_commands.py

@@ -310,6 +310,7 @@ class MachCommands(CommandBase):
         return 0
 
     def install_rustfmt(self):
+        self.ensure_bootstrapped()
         with open(os.devnull, "w") as devnull:
             if self.call_rustup_run(["cargo", "fmt", "--version", "-q"],
                                     stderr=devnull) != 0: