When you attempt to run Chutney using a command like: ``` ./chutney configure networks/basic ``` it will print the following error message if it cannot find `tor` or `tor-gencert`: ``` Cannot find the tor-gencert binary at 'tor-gencert' for the command line 'tor-gencert --create-identity-key --passphrase-fd 0 <snip>'. Set the TOR_DIR environment variable to the directory containing tor-gencert. ``` Chutney (the Python code) does not actually use this `TOR_DIR` environment variable (it's only used by `tools/test-network.sh` and related scripts). Instead the error message should say that the user should set the `CHUTNEY_TOR` and `CHUTNEY_TOR_GENCERT` environment variables.