crash reporter: send traceback for full chain of exceptions

Previously if there was a chain of exceptions, we were only
sending the traceback for the final exception.

E.g.
try:
    raise ExcOne("asdasd")
except ExcOne() as e:
    raise ExcTwo("qweqwe") from e

^ we would lose all info about ExcOne, including potentially many lines of trace

electrum/base_crash_reporter.py

@@ -81,7 +81,7 @@ class BaseCrashReporter(Logger):
     def get_traceback_info(self):
         exc_string = str(self.exc_args[1])
         stack = traceback.extract_tb(self.exc_args[2])
-        readable_trace = "".join(traceback.format_list(stack))
+        readable_trace = self.__get_traceback_str_to_send()
         id = {
             "file": stack[-1].filename,
             "name": stack[-1].name,
@@ -109,12 +109,19 @@ class BaseCrashReporter(Logger):
             pass
         return args
 
-    def _get_traceback_str(self) -> str:
+    def __get_traceback_str_to_send(self) -> str:
+        # make sure that traceback sent to crash reporter contains
+        # e.__context__ and e.__cause__, i.e. if there was a chain of
+        # exceptions, we want the full traceback for the whole chain.
         return "".join(traceback.format_exception(*self.exc_args))
 
+    def _get_traceback_str_to_display(self) -> str:
+        # overridden in Qt subclass
+        return self.__get_traceback_str_to_send()
+
     def get_report_string(self):
         info = self.get_additional_info()
-        info["traceback"] = self._get_traceback_str()
+        info["traceback"] = self._get_traceback_str_to_display()
         return self.issue_template.format(**info)
 
     def get_user_description(self):

electrum/gui/qt/exception_window.py

@@ -145,11 +145,11 @@ class Exception_Window(BaseCrashReporter, QWidget, MessageBoxMixin, Logger):
         wallet_types = Exception_Hook._INSTANCE.wallet_types_seen
         return ",".join(wallet_types)
 
-    def _get_traceback_str(self) -> str:
+    def _get_traceback_str_to_display(self) -> str:
         # The msg_box that shows the report uses rich_text=True, so
         # if traceback contains special HTML characters, e.g. '<',
         # they need to be escaped to avoid formatting issues.
-        traceback_str = super()._get_traceback_str()
+        traceback_str = super()._get_traceback_str_to_display()
         return html.escape(traceback_str)