There are multiple open issues in github about csh and quoting, also
on StackOverflow and else.
With normal settings (use_shell=True, shell_escape=True), a command that has
env.env_vars is wrapped and handed to the csh as:
/bin/bash -l -c "export FOO=\"bar\" && actual-command"
If in the csh setting backslash_quote is not set, csh does not handle the \"
as expected, but reads the command line as (one line per arg):
... and chokes on the final "