Fix confusing error when unpack fails due to network error

Before: `Error: .`
After: `Error: Failed downloading http://bad_url`

1 files changed, 3 insertions, 2 deletions

diff --git a/src/luarocks/fetch.lua b/src/luarocks/fetch.lua
index 980c8fe2..497ae84f 100644
--- a/src/luarocks/fetch.lua
+++ b/src/luarocks/fetch.lua
@@ -319,9 +319,10 @@ function fetch.get_sources(rockspec, extract, dest_dir)
    local url = rockspec.source.url
    local name = rockspec.name.."-"..rockspec.version
    local filename = rockspec.source.file
-   local source_file, store_dir, err, errcode
+   local source_file, store_dir
+   local ok, err, errcode
    if dest_dir then
-      local ok, err = fs.change_dir(dest_dir)
+      ok, err = fs.change_dir(dest_dir)
       if not ok then return nil, err, "dest_dir" end
       source_file, err, errcode = fetch.fetch_url(url, filename)
       fs.pop_dir()