gnu: Add python-pyrdfa3.

* gnu/packages/rdf.scm (python-pyrdfa3): New variable.

gnu/packages/rdf.scm

@@ -471,6 +471,43 @@ (define-public hdt-cpp
 C++ library as well as various command-line tools to to work with HDT.")
 (license license:lgpl2.1+)))
 
+(define-public python-pyrdfa3
+  (package
+    (name "python-pyrdfa3")
+    (version "3.5.3")
+    (source
+     (origin
+       (method url-fetch)
+       (uri (pypi-uri "pyRdfa3" version))
+       (sha256
+        (base32 "1biif5lav3gswkhjzq882s4rgxzmvwsy5gb9dxdk9pw75fln6xhm"))))
+    (build-system python-build-system)
+    (arguments
+     (list
+      #:tests? #f                       ;no test suite
+      #:phases
+      #~(modify-phases %standard-phases
+          (add-after 'unpack 'fix-python-3-issues
+            (lambda _
+              ;; Delete files that appear to be versions for older Pythons;
+              ;; they fail to byte compile (see:
+              ;; https://github.com/RDFLib/pyrdfa3/issues/41).
+              (with-directory-excursion "pyRdfaExtras/serializers"
+                (for-each delete-file
+                          (list "prettyXMLserializer_3.py"
+                                "prettyXMLserializer_3_2.py")))
+              ;; See https://github.com/RDFLib/pyrdfa3/issues/42.
+              (substitute* "pyRdfaExtras/__init__.py"
+                (("from StringIO import StringIO")
+                 "from io import StringIO")))))))
+    (propagated-inputs (list python-html5lib python-rdflib))
+    (home-page "https://www.w3.org/2012/pyRdfa/")
+    (synopsis "RDFa Python distiller/parser library")
+    (description "This library can extract RDFa 1.1 from (X)HTML, SVG, or XML.
+It can produce serialized versions of the extracted graph, or an RDFLib
+Graph.")
+    (license license:bsd-3)))
+
 (define-public python-sparqlwrapper
   (package
     (name "python-sparqlwrapper")