BaseTools/EdkLogger: Support unit tests with a SILENT log level

This allows the unit tests to run without the errors logging to the
screen.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Yingke Liu <yingke.d.liu@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17692 6f19259b-4bc3-4df7-8a09-765794883524

BaseTools/Source/Python/Common/EdkLogger.py

@@ -1,7 +1,7 @@
 ## @file
 # This file implements the log mechanism for Python tools.
 #
-# Copyright (c) 2007 - 2014, Intel Corporation. All rights reserved.<BR>
+# Copyright (c) 2007 - 2015, Intel Corporation. All rights reserved.<BR>
 # This program and the accompanying materials
 # are licensed and made available under the terms and conditions of the BSD License
 # which accompanies this distribution.  The full text of the license may be found at
@@ -32,6 +32,7 @@ INFO    = 20
 WARN    = 30
 QUIET   = 40
 ERROR   = 50
+SILENT  = 99
 
 IsRaiseError = True
 
@@ -39,7 +40,9 @@ IsRaiseError = True
 _ToolName = os.path.basename(sys.argv[0])
 
 # For validation purpose
-_LogLevels = [DEBUG_0, DEBUG_1, DEBUG_2, DEBUG_3, DEBUG_4, DEBUG_5, DEBUG_6, DEBUG_7, DEBUG_8, DEBUG_9, VERBOSE, WARN, INFO, ERROR, QUIET]
+_LogLevels = [DEBUG_0, DEBUG_1, DEBUG_2, DEBUG_3, DEBUG_4, DEBUG_5,
+              DEBUG_6, DEBUG_7, DEBUG_8, DEBUG_9, VERBOSE, WARN, INFO,
+              ERROR, QUIET, SILENT]
 
 # For DEBUG level (All DEBUG_0~9 are applicable)
 _DebugLogger = logging.getLogger("tool_debug")
@@ -235,6 +238,10 @@ def SetLevel(Level):
     _InfoLogger.setLevel(Level)
     _ErrorLogger.setLevel(Level)
 
+def InitializeForUnitTest():
+    Initialize()
+    SetLevel(SILENT)
+
 ## Get current log level
 def GetLevel():
     return _InfoLogger.getEffectiveLevel()