Make sure that get_timer works if Qt is not installed

glue/backends.py

@@ -22,6 +22,19 @@ def start(self):
         pass
 
 
+class SimpleTimer(TimerBase):
+
+    def __init__(self, interval, callback):
+        from threading import Timer
+        self._timer = Timer(interval / 1000., callback)
+
+    def start(self):
+        self._timer.start()
+
+    def stop(self):
+        self._timer.cancel()
+
+
 class QtTimer(TimerBase):
 
     def __init__(self, interval, callback):
@@ -37,12 +50,13 @@ def stop(self):
         self._timer.stop()
 
 
-def get_timer(backend='qt'):
-
-    if backend == 'qt':
-        return QtTimer
+def get_timer():
+    try:
+        from qtpy import QtCore
+    except ImportError:
+        return SimpleTimer
     else:
-        raise ValueError("Only QT Backend supported")
+        return QtTimer
 
 
 def get_backend(backend='qt'):

glue/core/data_factories/tests/test_data_factories.py

@@ -213,8 +213,6 @@ def test_data_reload_shape_change():
     assert d.coords is coords_old
 
 
-# TODO: this doesn't belong in the core since it relies on Qt
-@requires_qt
 def test_file_watch():
     cb = MagicMock()
     with make_file(b'test', 'csv') as fname:
@@ -232,7 +230,6 @@ def test_file_watch():
         assert cb.call_count == 1
 
 
-@requires_qt
 @pytest.mark.skipif(sys.platform.startswith('win'), reason='file deletion doesn\'t work on Windows')
 def test_file_watch_os_error():
     cb = MagicMock()