gnu: ensure pip and setuptools are installed even for Python 2.

* gnu/packages/python.scm (python-2.7): Add "--with-ensurepip=install" to
  configure-flags.
* doc/guix.texi (Python Modules): Document it.

doc/guix.texi

@@ -13579,7 +13579,6 @@ for instance, the module python-dateutil is packaged under the names
 starts with @code{py} (e.g. @code{pytz}), we keep it and prefix it as
 described above.
 
-
 @subsubsection Specifying Dependencies
 @cindex inputs, for Python packages
 
@@ -13595,6 +13594,11 @@ following check list to determine which dependency goes where.
 
 @itemize
 
+@item
+We currently package Python 2 with @code{setuptools} and @code{pip}
+installed like Python 3.4 has per default.  Thus you don't need to
+specify either of these as an input.
+
 @item
 Python dependencies required at run time go into
 @code{propagated-inputs}.  They are typically defined with the
@@ -13609,8 +13613,7 @@ testing---e.g., those in @code{tests_require}---go into
 propagated because they are not needed at run time, and (2) in a
 cross-compilation context, it's the ``native'' input that we'd want.
 
-Examples are @code{setuptools}, which is usually needed only at build
-time, or the @code{pytest}, @code{mock}, and @code{nose} test
+Examples are the @code{pytest}, @code{mock}, and @code{nose} test
 frameworks.  Of course if any of these packages is also required at
 run-time, it needs to go to @code{propagated-inputs}.
 

gnu/packages/python.scm

@@ -162,6 +162,7 @@
        #:configure-flags
        (list "--enable-shared"                    ;allow embedding
              "--with-system-ffi"                  ;build ctypes
+             "--with-ensurepip=install"           ;install pip and setuptools
              (string-append "LDFLAGS=-Wl,-rpath="
                             (assoc-ref %outputs "out") "/lib"))