Post MDEV-11902 Fix test failures in maria and myisam storage engines

my_readline can fail due to missing file. Make my_readline report this
condition separately so that we can catch it and report an appropriate
error message to the user.

mysql-test/r/myisam-system.result

@@ -5,7 +5,7 @@ Warnings:
 Warning	2	Can't find file: './test/t1.MYI' (errno: 2 "No such file or directory")
 create table t1 (a int) engine=myisam;
 select * from t1;
-ERROR HY000: Can't find file: './test/t1.MYI' (errno: 20 "Not a directory")
+ERROR HY000: Can't find file: './test/t1.MYI' (errno: 2 "No such file or directory")
 drop table t1;
 Warnings:
 Warning	2	Can't find file: './test/t1.MYI' (errno: 2 "No such file or directory")

mysql-test/suite/federated/federated_bug_35333.result

@@ -24,9 +24,9 @@ CREATE TABLE t1 (c1 int) ENGINE=MYISAM;
 SELECT TABLE_SCHEMA, TABLE_NAME, TABLE_TYPE, ENGINE, ROW_FORMAT, TABLE_ROWS, DATA_LENGTH, TABLE_COMMENT
 FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = 't1';
 TABLE_SCHEMA	TABLE_NAME	TABLE_TYPE	ENGINE	ROW_FORMAT	TABLE_ROWS	DATA_LENGTH	TABLE_COMMENT
-test	t1	BASE TABLE	NULL	NULL	NULL	NULL	Can't find file: './test/t1.MYI' (errno: 2 "Not a directory")
+test	t1	BASE TABLE	NULL	NULL	NULL	NULL	Can't find file: './test/t1.MYI' (errno: 2 "No such file or directory")
 Warnings:
-Warning	1017	Can't find file: './test/t1.MYI' (errno: 2 "Not a directory")
+Warning	1017	Can't find file: './test/t1.MYI' (errno: 2 "No such file or directory")
 DROP TABLE t1;
 Warnings:
 Warning	2	Can't find file: './test/t1.MYI' (errno: 2 "No such file or directory")

mysql-test/t/symlink-myisam-11902.test

@@ -49,7 +49,7 @@ exec rm -r $MYSQLTEST_VARDIR/tmp/foo;
 exec ln -s $datadir/mysql $MYSQLTEST_VARDIR/tmp/foo;
 set debug_sync='now SIGNAL run';
 connection default;
-replace_regex / '.*\/tmp\// 'MYSQLTEST_VARDIR\/tmp\// /31/20/;
+replace_regex / '.*\/test\// '.\/test\// /31/20/;
 error ER_FILE_NOT_FOUND;
 reap;
 flush tables;

mysys/my_symlink.c

@@ -129,6 +129,11 @@ int my_is_symlink(const char *filename __attribute__((unused)))
 
   to is guaranteed to never set to a string longer than FN_REFLEN
   (including the end \0)
+
+  On error returns -1, unless error is file not found, in which case it
+  is 1.
+
+  Sets my_errno to specific error number.
 */
 
 int my_realpath(char *to, const char *filename, myf MyFlags)
@@ -154,7 +159,10 @@ int my_realpath(char *to, const char *filename, myf MyFlags)
     if (MyFlags & MY_WME)
       my_error(EE_REALPATH, MYF(0), filename, my_errno);
     my_load_path(to, filename, NullS);
-    result= -1;
+    if (my_errno == ENOENT)
+      result= 1;
+    else
+      result= -1;
   }
   DBUG_RETURN(result);
 #elif defined(_WIN32)

storage/maria/ma_open.c

@@ -298,6 +298,11 @@ MARIA_HA *maria_open(const char *name, int mode, uint open_flags)
   realpath_err= my_realpath(name_buff, fn_format(org_name, name, "",
                                                  MARIA_NAME_IEXT,
                                                  MY_UNPACK_FILENAME),MYF(0));
+  if (realpath_err > 0) /* File not found, no point in looking further. */
+  {
+    DBUG_RETURN(NULL);
+  }
+
   if (my_is_symlink(org_name) &&
       (realpath_err || mysys_test_invalid_symlink(name_buff)))
   {

storage/myisam/mi_open.c

@@ -104,6 +104,11 @@ MI_INFO *mi_open(const char *name, int mode, uint open_flags)
 
   realpath_err= my_realpath(name_buff,
                             fn_format(org_name,name,"",MI_NAME_IEXT,4),MYF(0));
+  if (realpath_err > 0) /* File not found, no point in looking further. */
+  {
+    DBUG_RETURN(NULL);
+  }
+
   if (my_is_symlink(org_name) &&
       (realpath_err || mysys_test_invalid_symlink(name_buff)))
   {