Cache Log Error Levels
The log messages in the cache drvier's is_supported calls are more suited for the debug level.
diff --git a/system/libraries/Cache/drivers/Cache_apc.php b/system/libraries/Cache/drivers/Cache_apc.php
index 127a220..a84e7d2 100644
--- a/system/libraries/Cache/drivers/Cache_apc.php
+++ b/system/libraries/Cache/drivers/Cache_apc.php
@@ -150,7 +150,7 @@
 	{
 		if ( ! extension_loaded('apc') OR ! (bool) @ini_get('apc.enabled'))
 		{
-			log_message('error', 'The APC PHP extension must be loaded to use APC Cache.');
+			log_message('debug', 'The APC PHP extension must be loaded to use APC Cache.');
 			return FALSE;
 		}
 
diff --git a/system/libraries/Cache/drivers/Cache_memcached.php b/system/libraries/Cache/drivers/Cache_memcached.php
index 35d9104..d2a3a48 100644
--- a/system/libraries/Cache/drivers/Cache_memcached.php
+++ b/system/libraries/Cache/drivers/Cache_memcached.php
@@ -240,7 +240,7 @@
 	{
 		if ( ! extension_loaded('memcached') && ! extension_loaded('memcache'))
 		{
-			log_message('error', 'The Memcached Extension must be loaded to use Memcached Cache.');
+			log_message('debug', 'The Memcached Extension must be loaded to use Memcached Cache.');
 			return FALSE;
 		}
 
diff --git a/system/libraries/Cache/drivers/Cache_redis.php b/system/libraries/Cache/drivers/Cache_redis.php
index 484f284..40823fc 100644
--- a/system/libraries/Cache/drivers/Cache_redis.php
+++ b/system/libraries/Cache/drivers/Cache_redis.php
@@ -168,7 +168,7 @@
 		}
 		else
 		{
-			log_message('error', 'The Redis extension must be loaded to use Redis cache.');
+			log_message('debug', 'The Redis extension must be loaded to use Redis cache.');
 			return FALSE;
 		}
 	}
diff --git a/system/libraries/Cache/drivers/Cache_wincache.php b/system/libraries/Cache/drivers/Cache_wincache.php
index d749978..80d3ac1 100644
--- a/system/libraries/Cache/drivers/Cache_wincache.php
+++ b/system/libraries/Cache/drivers/Cache_wincache.php
@@ -150,7 +150,7 @@
 	{
 		if ( ! extension_loaded('wincache'))
 		{
-			log_message('error', 'The Wincache PHP extension must be loaded to use Wincache Cache.');
+			log_message('debug', 'The Wincache PHP extension must be loaded to use Wincache Cache.');
 			return FALSE;
 		}