Try to get the project source into a better, predictable location

.circleci/config.yml

@@ -78,14 +78,15 @@ jobs:
       WHEELHOUSE_PATH: &WHEELHOUSE_PATH "/tmp/wheelhouse"
       PIP_FIND_LINKS: "file:///tmp/wheelhouse"
 
+    # pip cannot install packages if the working directory is not readable.
+    # We want to run a lot of steps as nobody instead of as root.
+    working_directory: "/tmp"
+
     steps:
       - "checkout"
 
       - run: &SETUP_VIRTUALENV
           name: "Setup virtualenv"
-          # pip cannot install packages if the working directory is not
-          # readable.
-          working_directory: "/tmp"
           command: |
             sudo --set-home -u nobody /tmp/project/.circleci/setup-virtualenv.sh \
                 "${TAHOE_LAFS_TOX_ENVIRONMENT}" \