patch 8.2.4653: "import autoload" does not check the file name

Problem:    "import autoload" does not check the file name.
Solution:   Give an error if the file is not readable. (closes #10049)
diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index c5e96bd..c12f151 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -8386,7 +8386,7 @@
     // with Unix it is possible to open a directory
     if (mch_isdir(fname))
     {
-	semsg(_(e_src_is_directory), fname);
+	semsg(_(e_str_is_directory), fname);
 	return NULL;
     }
 #endif