+This library provides an exception-less interface to *unix-ish*
+operating systems. As usual, this means all flavors of POSIX-compliant
+systems, like Linux, *BSD, Mac OSX, and partially MS Windows.
+The module `Pvem_lwt_unix` contains the following sub-modules:
+- **Deferred_result** which is `Pvem.With_deferred(Lwt)`, i.e., basic
+ functions for manipulating `('ok, 'error) Pvem.Result.t Lwt.t`,
+- **IO** which implements the `IO` module type,
+- **System** implements the `SYSTEM` module type.
+You may run the tests, but you must have *Core* installed.
+Note that `system_test.ml` expects to be run as non-root (because it
+uses the fact that some paths are not writable to check access-rights