Add test for onerror keyword.

test/file.jl

@@ -859,7 +859,7 @@ end
 #     walkdir     #
 ###################
 
-dir = mktempdir()
+walkdir = mktempdir()
 cd(dir) do
     for i=1:2
         mkdir("sub_dir$i")
@@ -932,8 +932,29 @@ cd(dir) do
         @test dirs == ["sub_dir1", "sub_dir2"]
         @test files == ["file1", "file2"]
     end
+    #test of error handling
+    task_error = walkdir(".")
+    task_noerror = walkdir(".", onerror=x->x)
+    root, dirs, files = consume(task_error)
+    @test root == "."
+    @test dirs == ["sub_dir1", "sub_dir2"]
+    @test files == ["file1", "file2"]
+
+    rm(joinpath("sub_dir1"), recursive=true)
+    @test_throws SystemError consume(task_error) # throws an error because sub_dir1 do not exist
+
+    root, dirs, files = consume(task_noerror)
+    @test root == "."
+    @test dirs == ["sub_dir1", "sub_dir2"]
+    @test files == ["file1", "file2"]
+
+    root, dirs, files = consume(task_noerror) # skips sub_dir1 as it no longer exist
+    @test root == joinpath(".", "sub_dir2")
+    @test dirs == []
+    @test files == ["file_dir2"]
+
 end
-@unix_only rm(dir, recursive=true)
+@unix_only rm(walkdir, recursive=true)
 
 ############
 # Clean up #