Make DirectoryMonitor pausable using the with statement

lib/tfw/components/directory_monitor.py

@@ -42,3 +42,15 @@ class DirectoryMonitor:
     def stop(self):
         self.observer.stop()
         self.observer.join()
+
+    @property
+    def pauser(self):
+        return DirectoryMonitor.Pauser(self)
+
+    class Pauser:
+        def __init__(self, directory_monitor):
+            self.directorymonitor = directory_monitor
+        def __enter__(self):
+            self.directorymonitor.pause()
+        def __exit__(self, exc_type, exc_val, exc_tb):
+            self.directorymonitor.resume()

lib/tfw/components/source_code_event_handler.py

@@ -68,11 +68,10 @@ class SourceCodeEventHandler(EventHandlerBase, SupervisorMixin):
         return data
 
     def write(self, data):
-        self.monitor.pause()
-        try: self.filemanager.file_contents = data['content']
-        except Exception: log.exception('Error writing file!')
-        self.restart_process()
-        self.monitor.resume()
+        with self.monitor.pauser:
+            try: self.filemanager.file_contents = data['content']
+            except Exception: log.exception('Error writing file!')
+            self.restart_process()
         return data
 
     def select(self, data):