gnu: Add python2-keyring.

* gnu/packages/python.scm (python2-keyring): New variable.

gnu: Add python2-pyflakes and fix python2-pyflakes-0.8.1.

* gnu/packages/python.scm (python2-pyflakes): New variable.
* gnu/packages/python.scm (python2-pyflakes-0.8.1): Fix the definition.

gnu: Add python-prettytable

* gnu/packages/python.scm (python-prettytable,
  python2-prettytable): New variables.

gnu: Add R/qtl.

* gnu/packages/bioinformatics.scm (r-qtl): New variable.

Co-authored-by: Pjotr Prins <pjotr.guix@thebird.nl>

gnu: libmtp: Add additional MTP devices.

* gnu/packages/patches/libmtp-devices.patch: New file.
* gnu-system.am (dist_patch_DATA): Register patch.
* gnu/packages/patches/libmtp-devices.patch (libmtp)[source]: Add patch.

gnu: Add bioruby.

* gnu/packages/bioinformatics.scm (bioruby): New variable.

gnu: Add ruby-libxml.

* gnu/packages/ruby.scm (ruby-libxml): New variable.

gnu: Add ruby-shindo.

* gnu/packages/ruby.scm (ruby-shindo): New variable.

gnu: Add ruby-formatador.

* gnu/packages/ruby.scm (ruby-formatador): New variable.

gnu: Add ruby-notiffany.

* gnu/packages/ruby.scm (ruby-notiffany): New variable.

gnu: Add ruby-shellany.

* gnu/packages/ruby.scm (ruby-shellany): New variable.

gnu: Add ruby-nenv.

* gnu/packages/ruby.scm (ruby-nenv): New variable.

gnu: Add ruby-lumberjack.

* gnu/packages/ruby.scm (ruby-lumberjack): New variable.

gnu: Add ruby-docile.

* gnu/packages/ruby.scm (ruby-docile): New variable.

gnu: ifstatus: Fix license.

* gnu/packages/networking.scm (ifstatus)[license]: Set to GPL2+.

lint: Report lonely parentheses.

* guix/scripts/lint.scm (%hanging-paren-rx): New variable.
  (report-lone-parentheses): New procedure.
  (%formatting-reporters): Use it.
* tests/lint.scm ("formatting: lonely parentheses"): New test.

gnu: Add ifstatus.

* gnu/packages/networking.scm (ifstatus): New variable.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

store: Add 'set-build-options*'.

Suggested by: Ludovic Courtès <ludo@gnu.org>.

* guix/store.scm (set-build-options*): New procedure.

ui: Add 'show-derivation-outputs'.

* guix/scripts/build.scm (guix-build): Extract code from here and move to...
* guix/ui.scm (show-derivation-outputs): ... here.  New procedure.

Add (guix scripts).

* guix/ui.scm: Add missing copyright lines.
  (args-fold*, environment-build-options, %default-argument-handler,
  parse-command-line): Move to ...
* guix/scripts.scm: ...here.  New file.
* guix/scripts/archive.scm: Use it.
* guix/scripts/build.scm: Likewise.
* guix/scripts/download.scm: Likewise.
* guix/scripts/edit.scm: Likewise.
* guix/scripts/environment.scm: Likewise.
* guix/scripts/gc.scm: Likewise.
* guix/scripts/graph.scm: Likewise.
* guix/scripts/hash.scm: Likewise.
* guix/scripts/import/cpan.scm: Likewise.
* guix/scripts/import/cran.scm: Likewise.
* guix/scripts/import/elpa.scm: Likewise.
* guix/scripts/import/gem.scm: Likewise.
* guix/scripts/import/gnu.scm: Likewise.
* guix/scripts/import/hackage.scm: Likewise.
* guix/scripts/import/nix.scm: Likewise.
* guix/scripts/import/pypi.scm: Likewise.
* guix/scripts/lint.scm: Likewise.
* guix/scripts/package.scm: Likewise.
* guix/scripts/publish.scm: Likewise.
* guix/scripts/pull.scm: Likewise.
* guix/scripts/refresh.scm: Likewise.
* guix/scripts/size.scm: Likewise.
* guix/scripts/system.scm: Likewise.
* tests/ui.scm (with-environment-variable, "parse-command-line",
  "parse-command-line and --no options"): Move to ...
* tests/scripts.scm: ...here.  New file.
* Makefile.am (MODULES): Add guix/scripts.scm.
  (SCM_TESTS): Add tests/scripts.scm.
* po/guix/POTFILES.in: Add guix/scripts.scm.