gnu: Add python2-rdflib.

* gnu/packages/rdf.scm (python2-rdflib): New variable.
  (python-rdflib): Add patch.
* gnu/packages/patches/python2-rdflib-drop-sparqlwrapper.patch: New file.
* gnu-system.am (dist_patch_DATA): Register patch.

gnu-system.am

@@ -479,6 +479,7 @@ dist_patch_DATA =						\
   gnu/packages/patches/python-fix-tests.patch			\
   gnu/packages/patches/python-libffi-mips-n32-fix.patch		\
   gnu/packages/patches/python-sqlite-3.8.4-test-fix.patch	\
+  gnu/packages/patches/python2-rdflib-drop-sparqlwrapper.patch	\
   gnu/packages/patches/python2-sqlite-3.8.4-test-fix.patch	\
   gnu/packages/patches/python2-pygobject-2-gi-info-type-error-domain.patch \
   gnu/packages/patches/qt4-tests.patch				\

gnu/packages/patches/python2-rdflib-drop-sparqlwrapper.patch

@@ -0,0 +1,16 @@
+Drop SPARQLWrapper from the required install inputs under Python 2, as it
+creates a circular dependency.
+
+diff -u rdflib-4.1.2.alt/setup.py rdflib-4.1.2/setup.py
+--- rdflib-4.1.2.alt/setup.py	2014-03-04 12:40:26.000000000 +0100
++++ rdflib-4.1.2/setup.py	2015-01-23 21:52:59.000000000 +0100
+@@ -52,7 +52,7 @@
+         kwargs['test_suite'] = "nose.collector"
+         kwargs['install_requires'] = [
+             'isodate',
+-            'pyparsing', 'SPARQLWrapper']
++            'pyparsing']
+ 
+         if sys.version_info[1]<7:  # Python 2.6
+             kwargs['install_requires'].append('ordereddict')
+

gnu/packages/rdf.scm

@@ -319,6 +319,9 @@ system.")
               "https://pypi.python.org/packages/source/r/rdflib/rdflib-"
               version
               ".tar.gz"))
+        (patches
+          ;; The patch has no effect under Python 3.
+          (list (search-patch "python2-rdflib-drop-sparqlwrapper.patch")))
         (sha256
           (base32
             "0kvaf332cqbi47rqzlpdx4mbkvw12mkrzkj8n9l19wk713d4py9w"))))
@@ -336,3 +339,13 @@ system.")
 powerful language for representing information.")
     (license (bsd-style "file://LICENSE"
                         "See LICENSE in the distribution."))))
+
+(define-public python2-rdflib
+  (let ((base (package-with-python2 python-rdflib)))
+    (package
+      (inherit base)
+      (inputs
+        (append (package-inputs base)
+                `(("python2-nose" ,python2-nose))))
+      (arguments
+        `(#:tests? #f))))) ; 3 tests fail, also outside Guix