mllib: Create a common utility function is_directory.

This is a wrapper around Sys.is_directory which doesn't throw
exceptions.

builder/cache.ml

@@ -34,13 +34,8 @@ type t = {
 }
 
 let create ~debug ~directory =
-  (* Annoyingly Sys.is_directory throws an exception on failure
-   * (RHBZ#1022431).
-   *)
-  let is_dir = try Sys.is_directory directory with Sys_error _ -> false in
-  if is_dir = false then (
-    mkdir directory 0o755
-  );
+  if not (is_directory directory) then
+    mkdir directory 0o755;
   {
     debug = debug;
     directory = directory;

mllib/common_utils.ml

@@ -451,3 +451,10 @@ let is_block_device file =
 let is_char_device file =
   try (Unix.stat file).Unix.st_kind = Unix.S_CHR
   with Unix.Unix_error _ -> false
+
+(* Annoyingly Sys.is_directory throws an exception on failure
+ * (RHBZ#1022431).
+ *)
+let is_directory path =
+  try Sys.is_directory path
+  with Sys_error _ -> false

v2v/cmdline.ml

@@ -181,9 +181,7 @@ read the man page virt-v2v(1).
     | `Local ->
       if output_storage = "" then
         error (f_"-o local: output directory was not specified, use '-os /dir'");
-      let dir_exists =
-        try Sys.is_directory output_storage with Sys_error _ -> false in
-      if not dir_exists then
+      if not (is_directory output_storage) then
         error (f_"-os %s: output directory does not exist or is not a directory")
           output_storage;
       OutputLocal output_storage