[FIX] hw_proxy: error when check status in debug mode

when access status hw_proxy in debug mode it's will raise error,
it's happens because hw_proxy uses subprocess module to get a list of usb
but the subprocess module not imported.

Introduced at 56456359

Closes #18820

addons/hw_proxy/controllers/main.py

@@ -4,6 +4,7 @@
 import commands
 import logging
 import time
+import subprocess
 from threading import Lock
 
 
@@ -22,7 +23,7 @@ BANNED_DEVICES = set([
 ])
 
 
-# drivers modules must add to drivers an object with a get_status() method 
+# drivers modules must add to drivers an object with a get_status() method
 # so that 'status' can return the status of all active drivers
 drivers = {}
 
@@ -107,7 +108,7 @@ class Proxy(http.Controller):
             if not (device_id in BANNED_DEVICES):
             	resp+= "<div class='device' data-device='"+device+"'>"+device_name+"</div>\n"
                 count += 1
-        
+
         if count == 0:
             resp += "<div class='device'>No USB Device Found</div>"
 
@@ -125,7 +126,7 @@ class Proxy(http.Controller):
             """ % subprocess.check_output('lsusb -v', shell=True)
 
         return request.make_response(resp,{
-            'Cache-Control': 'no-cache', 
+            'Cache-Control': 'no-cache',
             'Content-Type': 'text/html; charset=utf-8',
             'Access-Control-Allow-Origin':  '*',
             'Access-Control-Allow-Methods': 'GET',
@@ -166,7 +167,7 @@ class Proxy(http.Controller):
     @http.route('/hw_proxy/payment_request', type='json', auth='none', cors='*')
     def payment_request(self, price):
         """
-        The PoS will activate the method payment 
+        The PoS will activate the method payment
         """
         print "payment_request: price:"+str(price)
         return 'ok'
@@ -174,7 +175,7 @@ class Proxy(http.Controller):
     @http.route('/hw_proxy/payment_status', type='json', auth='none', cors='*')
     def payment_status(self):
         print "payment_status"
-        return { 'status':'waiting' } 
+        return { 'status':'waiting' }
 
     @http.route('/hw_proxy/payment_cancel', type='json', auth='none', cors='*')
     def payment_cancel(self):
@@ -206,12 +207,12 @@ class Proxy(http.Controller):
 
     @http.route('/hw_proxy/is_scanner_connected', type='json', auth='none', cors='*')
     def is_scanner_connected(self, receipt):
-        print 'is_scanner_connected?' 
+        print 'is_scanner_connected?'
         return False
 
     @http.route('/hw_proxy/scanner', type='json', auth='none', cors='*')
     def scanner(self, receipt):
-        print 'scanner' 
+        print 'scanner'
         time.sleep(10)
         return ''