Manage logs when log file is not accessible

Fixes #25

If the default log file location is not accessile, inform user
about the error (e.g., no write permission, location does not
exist). Also, make non-debug log messages shorter and make sure
all instructions and warnings are printed to standard error.

kamaki/cli/logger.py

-# Copyright 2013 GRNET S.A. All rights reserved.
+# Copyright 2013-2014 GRNET S.A. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or
 # without modification, are permitted provided that the following
@@ -33,6 +33,7 @@
 
 from os import chmod
 from os.path import expanduser
+from sys import stderr
 import logging
 
 
@@ -69,10 +70,15 @@ def get_log_filename():
             with open(logfile, 'a+') as f:
                 f.seek(0)
             chmod(logfile, 0600)
-        except IOError:
+        except IOError as e:
+            stderr.write(
+                'WARNING: Failed to use file "%s" for logging\n' % logfile)
+            stderr.write('\t%s\n' % e)
+            stderr.flush()
             continue
         return logfile
-    print('Failed to open any logging locations, file-logging aborted')
+    stderr.write('WARNING: No valid log files, redirect logs to std err\n')
+    stderr.flush()
 
 
 def set_log_filename(filename):
@@ -94,9 +100,10 @@ def _add_logger(name, level=None, filename=None, fmt=None):
 @if_logger_enabled
 def add_file_logger(name, level=None, filename=None):
     try:
+        fmt = '%(name)s(%(levelname)s) %(asctime)s\n  %(message)s' if (
+            level == logging.DEBUG) else '%(name)s: %(message)s'
         return _add_logger(
-            name, level, filename or get_log_filename(),
-            fmt='%(name)s(%(levelname)s) %(asctime)s\n\t%(message)s')
+            name, level, filename or get_log_filename(), fmt=fmt)
     except Exception:
         return get_logger(name)
 

kamaki/cli/test.py

-# Copyright 2013 GRNET S.A. All rights reserved.
+# Copyright 2013-2014 GRNET S.A. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or
 # without modification, are permitted provided that the following
@@ -250,9 +250,12 @@ class LoggerMethods(TestCase):
             for name, level, filename in product(
                     ('my name'), ('my level', None), ('my filename', None)):
                 self.assertEqual(add_file_logger(name, level, filename), 'AL')
+                from logging import DEBUG as dbg
+                fmt = '%(name)s(%(levelname)s) %(asctime)s\n\t%(message)s' if (
+                    level == dbg) else '%(name)s: %(message)s'
                 self.assertEqual(AL.mock_calls[-1], call(
                     name, level, filename or 'my log fname',
-                    fmt='%(name)s(%(levelname)s) %(asctime)s\n\t%(message)s'))
+                    fmt=fmt))
                 if filename:
                     self.assertEqual(GLFcount, GLF.call_count)
                 else: