Docs: Remove requirement for `python-future`.

This Python module was used nowhere and would not make much sense
either: The code is for Python 3.7 which is the most current version
of Python and there is no "future" to "backport" to 3.7.

README

@@ -75,7 +75,6 @@ These are the dependencies for GNUnet's testsuite:
 - Posix Shell                       (for some tests)
 - Bash                              (for some tests[*4])
 - python             >= 3.7         (only python 3.7 is supported)
-- python-future      >= 3.7         (only python 3.7 is supported)
 - base tools
   - mostly:
     - which,
@@ -428,8 +427,8 @@ $ make install
 $ export $GNUNET_PREFIX=$SOMEWHERE
 $ make check
 
-Some of the testcases require python >= 3.7, and the python modules
-"python-future" (http://python-future.org/) and "pexpect" to be installed.
+Some of the testcases require python >= 3.7, and the python module
+"pexpect" to be installed.
 If any testcases fail to pass on your system, run
 "contrib/scripts/gnunet-bugreport" (in the repository) or "gnunet-bugreport"
 when you already have GNUnet installed and report its output together with

contrib/packages/guix/guix-env-py2.scm

@@ -102,7 +102,6 @@
          ("zlib" ,zlib)
          ("perl" ,perl)
          ("python-2" ,python-2) ; tests and gnunet-qr
-         ("python2-future" ,python2-future)
          ("jansson" ,jansson)
          ("nss" ,nss)
          ("glib" ,glib "bin")

contrib/packages/guix/notest-guix-env.scm

@@ -100,7 +100,6 @@
          ("zlib" ,zlib)
          ("perl" ,perl)
          ("python-2" ,python-2) ; tests and gnunet-qr
-         ("python2-future" ,python2-future)
          ("jansson" ,jansson)
          ("nss" ,nss)
          ("glib" ,glib "bin")

doc/handbook/chapters/installation.texi

@@ -90,7 +90,6 @@ These are the dependencies only required for certain features
 These are the test suite requirements:
 @itemize @bullet
 @item python3.7
-@item python3-7 future module
 @item gnunet (installation first)
 @item which(1)
 @item a shell (possibly Bash, maybe just POSIX sh)