wizard hw devices: only scan once

lib/base_wizard.py

@@ -202,12 +202,17 @@ class BaseWizard(object):
         # scan devices
         devices = []
         devmgr = self.plugins.device_manager
+        try:
+            scanned_devices = devmgr.scan_devices()
+        except BaseException as e:
+            devmgr.print_error('error scanning devices: {}'.format(e))
+        else:
             for name, description, plugin in support:
                 try:
                     # FIXME: side-effect: unpaired_device_info sets client.handler
-                u = devmgr.unpaired_device_infos(None, plugin)
-            except:
-                devmgr.print_error("error", name)
+                    u = devmgr.unpaired_device_infos(None, plugin, devices=scanned_devices)
+                except BaseException as e:
+                    devmgr.print_error('error getting device infos for {}: {}'.format(name, e))
                     continue
                 devices += list(map(lambda x: (name, x), u))
         if not devices: