Move signal handler setup to C++ layer

See man pages for sigaction(2), sigemptyset(3):
http://man7.org/linux/man-pages/man2/sigaction.2.html
https://linux.die.net/man/3/sigemptyset

Code loosely based on
https://gist.github.com/azadkuh/a2ac6869661ebd3f8588 .

main.cpp

@@ -2,14 +2,32 @@
 #include <QQmlApplicationEngine>
 #include <QQmlContext>
 #include <stdlib.h>
+#include <signal.h>
 #include <QtGlobal>
 #include <QtWidgets>
 #include <QQuickWindow>
 #include <QQuickStyle>
 #include "screenshot.h"
 
+void handleExitSignal(int sig) {
+  printf("Exiting due to signal %d\n", sig);
+  QCoreApplication::quit();
+}
+
+void setupUnixSignals() {
+  struct sigaction sa;
+  sa.sa_handler = handleExitSignal;
+  sigset_t signal_mask;
+  sigemptyset(&signal_mask);
+  sa.sa_mask = signal_mask;
+  sa.sa_flags = 0;
+  sigaction(SIGINT, &sa, nullptr);
+}
+
 int main(int argc, char *argv[])
 {
+    setupUnixSignals();
+
     // Don't write .pyc files.
     qputenv("PYTHONDONTWRITEBYTECODE", "1");
 

py/yubikey.py

@@ -23,7 +23,6 @@ from ykman.oath import (
 from ykman.otp import OtpController
 from ykman.settings import Settings
 from qr import qrparse, qrdecode
-import signal
 
 
 logger = logging.getLogger(__name__)
@@ -532,9 +531,3 @@ def init_with_logging(log_level, log_file=None):
 def init():
     global controller
     controller = Controller()
-
-    try:
-        # TODO: We should probably do this in the C++/QML layer instead
-        signal.signal(signal.SIGINT, signal.SIG_DFL)
-    except Exception as e:
-        logger.error('Failed to set signal handlers', exc_info=e)