In MySQL 5.5, the InnoDB Plugin is the default version and it's compiled in.
In this case, the plugin cannot be uninstalled and we get error when trying
to do so:

mysql> uninstall plugin innodb;
ERROR 1305 (42000): PLUGIN innodb does not exist

But the error message is misleading. The plugin does exist, it just cannot
be installed because it's not dynamically loaded.

MySQL bug report: http://bugs.mysql.com/bug.php?id=51771
MariaDB bug report: https://mariadb.atlassian.net/browse/MDEV-4573
MariaDB fix: http://bazaar.launchpad.net/~maria-captains/maria/5.5/revision/3802

diff --git a/include/mysql.h b/include/mysql.h
index 38b54de..0b13e92 100644
--- a/include/mysql.h
+++ b/include/mysql.h
@@ -134,6 +134,7 @@ typedef unsigned long long my_ulonglong;
 
 /* backward compatibility define - to be removed eventually */
 #define ER_WARN_DATA_TRUNCATED WARN_DATA_TRUNCATED
+#define WARN_PLUGIN_DELETE_BUILTIN ER_PLUGIN_DELETE_BUILTIN
 
 typedef struct st_mysql_rows {
   struct st_mysql_rows *next;		/* list of rows */
diff --git a/mysql-test/r/plugin.result b/mysql-test/r/plugin.result
index a3d7437..8ea475d 100644
--- a/mysql-test/r/plugin.result
+++ b/mysql-test/r/plugin.result
@@ -232,3 +232,5 @@ DROP PROCEDURE p_install;
 SET DEBUG_SYNC='RESET';
 disconnect con1;
 disconnect con2;
+UNINSTALL PLUGIN MyISAM;
+ERROR HY000: Built-in plugins cannot be deleted
diff --git a/mysql-test/t/plugin.test b/mysql-test/t/plugin.test
index de68d36..bf9fb7d 100644
--- a/mysql-test/t/plugin.test
+++ b/mysql-test/t/plugin.test
@@ -277,3 +277,9 @@ disconnect con1;
 disconnect con2;
 
 --disable_connect_log
+
+#
+# MDEV-4573 UNINSTALL PLUGIN misleading error message for non-dynamic plugins
+#
+--error ER_PLUGIN_DELETE_BUILTIN
+UNINSTALL PLUGIN MyISAM;
diff --git a/sql/share/errmsg-utf8.txt b/sql/share/errmsg-utf8.txt
index 15acc66..35e2c3c 100644
--- a/sql/share/errmsg-utf8.txt
+++ b/sql/share/errmsg-utf8.txt
@@ -6235,7 +6235,7 @@ WARN_NO_MASTER_INFO
 WARN_OPTION_IGNORED
   eng "<%-.64s> option ignored"
   ger "Option <%-.64s> ignoriert"
-WARN_PLUGIN_DELETE_BUILTIN
+ER_PLUGIN_DELETE_BUILTIN
   eng "Built-in plugins cannot be deleted"
   ger "Eingebaute Plugins können nicht gelöscht werden"
 WARN_PLUGIN_BUSY
diff --git a/sql/sql_plugin.cc b/sql/sql_plugin.cc
index f134e4f..7e34432 100644
--- a/sql/sql_plugin.cc
+++ b/sql/sql_plugin.cc
@@ -2008,9 +2008,7 @@ bool mysql_uninstall_plugin(THD *thd, const LEX_STRING *name)
   }
   if (!plugin->plugin_dl)
   {
-    push_warning(thd, Sql_condition::WARN_LEVEL_WARN,
-                 WARN_PLUGIN_DELETE_BUILTIN, ER(WARN_PLUGIN_DELETE_BUILTIN));
-    my_error(ER_SP_DOES_NOT_EXIST, MYF(0), "PLUGIN", name->str);
+    my_error(ER_PLUGIN_DELETE_BUILTIN, MYF(0));
     goto err;
   }
   if (plugin->load_option == PLUGIN_FORCE_PLUS_PERMANENT)