calculate_download_size may be used by a user but ctx.config.cached_packages_dir gives exception

pisi/operations/helper.py

@@ -80,6 +80,12 @@ def calculate_download_sizes(order):
     installdb = pisi.db.installdb.InstallDB()
     packagedb = pisi.db.packagedb.PackageDB()
 
+    try:
+        cached_packages_dir = ctx.config.cached_packages_dir()
+    except OSError:
+        # happens when cached_packages_dir tried to be created by an unpriviledged user
+        cached_packages_dir = None
+
     for pkg in [packagedb.get_package(name) for name in order]:
 
         delta = None
@@ -100,13 +106,13 @@ def calculate_download_sizes(order):
             pkg_hash = pkg.packageHash
             pkg_size = pkg.packageSize
 
-        path = util.join_path(ctx.config.cached_packages_dir(), fn)
-
-        # check the file and sha1sum to be sure it _is_ the cached package
-        if os.path.exists(path) and util.sha1_file(path) == pkg_hash:
-            cached_size += pkg_size
-        elif os.path.exists("%s.part" % path):
-            cached_size += os.stat("%s.part" % path).st_size
+        if cached_packages_dir:
+            path = util.join_path(cached_packages_dir, fn)
+            # check the file and sha1sum to be sure it _is_ the cached package
+            if os.path.exists(path) and util.sha1_file(path) == pkg_hash:
+                cached_size += pkg_size
+            elif os.path.exists("%s.part" % path):
+                cached_size += os.stat("%s.part" % path).st_size
 
         total_size += pkg_size