Merge pull request #960 from iansf/fix_ios_deploy_crashes

Avoid crashing when an iOS device isn't connected

packages/flutter/lib/sky_tool

@@ -465,6 +465,7 @@ class IOSDevice(object):
             return False
         if cls._is_connected:
             return True
+        try:
             cmd = [
                 'ios-deploy',
                 '--detect',
@@ -475,12 +476,15 @@ class IOSDevice(object):
             out = subprocess.check_output(cmd)
             match = re.search(r'\[\.\.\.\.\] Found [^\)]*\) connected', out)
             cls._is_connected = match is not None
+        except subprocess.CalledProcessError:
+            cls._is_connected = False
         return cls._is_connected
 
     @classmethod
     def install_app(cls, ios_app_path):
         if not cls.has_ios_deploy():
             return
+        try:
             cmd = [
                 'ios-deploy',
                 '--justlaunch',
@@ -491,11 +495,14 @@ class IOSDevice(object):
             ]
             logging.info(' '.join(cmd))
             subprocess.check_call(cmd)
+        except subprocess.CalledProcessError:
+            pass
 
     @classmethod
     def copy_file(cls, bundle_id, local_path, device_path):
         if not cls.has_ios_deploy():
             return
+        try:
             cmd = [
                 'ios-deploy',
                 '-t',
@@ -509,6 +516,8 @@ class IOSDevice(object):
             ]
             logging.info(' '.join(cmd))
             subprocess.check_call(cmd)
+        except subprocess.CalledProcessError:
+            pass
 
 
 class IOSSimulator(object):