wizard,hw: tell user about errors during plugin init

see #4817 (issuecomment-434765570)

electrum/plugin.py

@@ -28,7 +28,7 @@ import os
 import pkgutil
 import time
 import threading
-from typing import NamedTuple, Any, Union
+from typing import NamedTuple, Any, Union, TYPE_CHECKING, Optional
 
 from .i18n import _
 from .util import (profiler, PrintError, DaemonThread, UserCancelled,
@@ -37,6 +37,9 @@ from . import bip32
 from . import plugins
 from .simple_config import SimpleConfig
 
+if TYPE_CHECKING:
+    from .plugins.hw_wallet import HW_PluginBase
+
 
 plugin_loaders = {}
 hook_names = set()
@@ -148,10 +151,17 @@ class Plugins(DaemonThread):
                 try:
                     p = self.get_plugin(name)
                     if p.is_enabled():
-                        out.append([name, details[2], p])
-                except:
+                        out.append(HardwarePluginToScan(name=name,
+                                                        description=details[2],
+                                                        plugin=p,
+                                                        exception=None))
+                except Exception as e:
                     traceback.print_exc()
                     self.print_error("cannot load plugin for:", name)
+                    out.append(HardwarePluginToScan(name=name,
+                                                    description=details[2],
+                                                    plugin=None,
+                                                    exception=e))
         return out
 
     def register_wallet_type(self, name, gui_good, wallet_type):
@@ -277,6 +287,13 @@ class DeviceInfo(NamedTuple):
     initialized: bool
 
 
+class HardwarePluginToScan(NamedTuple):
+    name: str
+    description: str
+    plugin: Optional['HW_PluginBase']
+    exception: Optional[Exception]
+
+
 class DeviceMgr(ThreadJob, PrintError):
     '''Manages hardware clients.  A client communicates over a hardware
     channel with the device.