correcting a bug when url and files are mixed

lib/spack/spack/cmd/md5.py

@@ -23,8 +23,10 @@
 # Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 ##############################################################################
 import os
-import hashlib
 import argparse
+import hashlib
+
+from contextlib import contextmanager
 
 import llnl.util.tty as tty
 from llnl.util.filesystem import *
@@ -34,6 +36,19 @@
 
 description = "Calculate md5 checksums for files/urls."
 
+@contextmanager
+def stager(url):
+    _cwd = os.getcwd()
+    _stager = Stage(url)
+    try:
+        _stager.fetch()
+        yield _stager
+    except FailedDownloadError:
+        tty.msg("Failed to fetch %s" % url)
+    finally:
+        _stager.destroy()
+        os.chdir(_cwd) # the Stage class changes the current working dir so it has to be restored
+
 def setup_parser(subparser):
     setup_parser.parser = subparser
     subparser.add_argument('files', nargs=argparse.REMAINDER,
@@ -46,17 +61,9 @@ def md5(parser, args):
 
     for f in args.files:
         if not os.path.isfile(f):
-            stage = Stage(f)
-            try:
-                stage.fetch()
+            with stager(f) as stage:
                 checksum = spack.util.crypto.checksum(hashlib.md5, stage.archive_file)
                 print "%s  %s" % (checksum, f)
-            except FailedDownloadError, e:
-                tty.msg("Failed to fetch %s" % url)
-                continue
-
-            finally:
-                stage.destroy()
         else:
             if not can_access(f):
                 tty.die("Cannot read file: %s" % f)