crash reporter: add EarlyExceptionsQueue

`util.send_exception_to_crash_reporter` is now useful and can be transparently
used even before the exception hook is set up.

electrum/base_crash_reporter.py

@@ -24,6 +24,7 @@ import json
 import locale
 import traceback
 import sys
+import queue
 
 from .version import ELECTRUM_VERSION
 from . import constants
@@ -131,6 +132,43 @@ class BaseCrashReporter(Logger):
         raise NotImplementedError
 
 
+class EarlyExceptionsQueue:
+    """Helper singleton for explicitly sending exceptions to crash reporter.
+
+    Typically the GUIs set up an "exception hook" that catches all otherwise
+    uncaught exceptions (which unroll the stack of a thread completely).
+    This class provides methods to report *any* exception, and queueing logic
+    that delays processing until the exception hook is set up.
+    """
+
+    _is_exc_hook_ready = False
+    _exc_queue = queue.Queue()
+
+    @classmethod
+    def set_hook_as_ready(cls):
+        if cls._is_exc_hook_ready:
+            return
+        cls._is_exc_hook_ready = True
+        while cls._exc_queue.qsize() > 0:
+            e = cls._exc_queue.get()
+            cls._send_exception_to_crash_reporter(e)
+
+    @classmethod
+    def send_exception_to_crash_reporter(cls, e: BaseException):
+        if cls._is_exc_hook_ready:
+            cls._send_exception_to_crash_reporter(e)
+        else:
+            cls._exc_queue.put(e)
+
+    @staticmethod
+    def _send_exception_to_crash_reporter(e: BaseException):
+        assert EarlyExceptionsQueue._is_exc_hook_ready
+        sys.excepthook(type(e), e, e.__traceback__)
+
+
+send_exception_to_crash_reporter = EarlyExceptionsQueue.send_exception_to_crash_reporter
+
+
 def trigger_crash():
     # note: do not change the type of the exception, the message,
     # or the name of this method. All reports generated through this