gui init: raise GuiImportError instead of sys.exit if dep is missing

electrum/__init__.py

@@ -11,6 +11,10 @@ if is_local and os.name == 'nt':
         os.add_dll_directory(os.path.dirname(__file__))
 
 
+class GuiImportError(ImportError):
+    pass
+
+
 from .version import ELECTRUM_VERSION
 from .util import format_satoshis
 from .wallet import Wallet

electrum/daemon.py

@@ -51,6 +51,7 @@ from .commands import known_commands, Commands
 from .simple_config import SimpleConfig
 from .exchange_rate import FxThread
 from .logging import get_logger, Logger
+from . import GuiImportError
 
 if TYPE_CHECKING:
     from electrum import gui
@@ -621,8 +622,11 @@ class Daemon(Logger):
         if gui_name in ['lite', 'classic']:
             gui_name = 'qt'
         self.logger.info(f'launching GUI: {gui_name}')
+        try:
             try:
                 gui = __import__('electrum.gui.' + gui_name, fromlist=['electrum'])
+            except GuiImportError as e:
+                sys.exit(str(e))
             self.gui_object = gui.ElectrumGui(config=config, daemon=self, plugins=plugins)
             if not self._stop_entered:
                 self.gui_object.main()

electrum/gui/kivy/__init__.py

@@ -29,16 +29,19 @@ import sys
 import os
 from typing import TYPE_CHECKING
 
+from electrum import GuiImportError
+
 KIVY_GUI_PATH = os.path.abspath(os.path.dirname(__file__))
 os.environ['KIVY_DATA_DIR'] = os.path.join(KIVY_GUI_PATH, 'data')
 
 try:
     sys.argv = ['']
     import kivy
-except ImportError:
+except ImportError as e:
     # This error ideally shouldn't be raised with pre-built packages
-    sys.exit("Error: Could not import kivy. Please install it using the "
-             "instructions mentioned here `https://kivy.org/#download` .")
+    raise GuiImportError(
+        "Error: Could not import kivy. Please install it using the "
+        "instructions mentioned here `https://kivy.org/#download` .") from e
 
 # minimum required version for kivy
 kivy.require('1.8.0')

electrum/gui/qt/__init__.py

@@ -30,12 +30,15 @@ import traceback
 import threading
 from typing import Optional, TYPE_CHECKING, List
 
+from electrum import GuiImportError
 
 try:
     import PyQt5
     import PyQt5.QtGui
-except Exception:
-    sys.exit("Error: Could not import PyQt5 on Linux systems, you may try 'sudo apt-get install python3-pyqt5'")
+except Exception as e:
+    raise GuiImportError(
+        "Error: Could not import PyQt5 on Linux systems, "
+        "you may try 'sudo apt-get install python3-pyqt5'") from e
 
 from PyQt5.QtGui import QGuiApplication
 from PyQt5.QtWidgets import (QApplication, QSystemTrayIcon, QWidget, QMenu,