Expose logging facilities to commands

All the subclass of the Command class can now use the
the class object `Command.log` for logging pourposes.
This is a standard `logging.Logger` instance, thus
the standard logging api must be used.

Example:

```
class dummy_cmd(Command):
    def execute(self):
        self.log.info("the dummy command has been invoked")
```

1 files changed, 5 insertions, 0 deletions

diff --git a/ranger/api/commands.py b/ranger/api/commands.py
index 9b8ec7d5..93c50adb 100644
--- a/ranger/api/commands.py
+++ b/ranger/api/commands.py
@@ -236,6 +236,11 @@ class Command(FileManagerAware):
                     break
         return flags, rest
 
+    @lazy_property
+    def log(self):
+        import logging
+        return logging.getLogger('ranger.commands.' + self.__class__.__name__)
+
     # XXX: Lazy properties? Not so smart? self.line can change after all!
     @lazy_property
     def _tabinsert_left(self):