gnu: Add python-snowballstemmer.

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

gnu/packages/python.scm

@@ -9727,3 +9727,25 @@ the default Sphinx theme.")
       (native-inputs
        `(("python2-setuptools" ,python2-setuptools)
          ,@(package-native-inputs base))))))
+
+(define-public python-snowballstemmer
+  (package
+    (name "python-snowballstemmer")
+    (version "1.2.1")
+    (source (origin
+              (method url-fetch)
+              (uri (pypi-uri "snowballstemmer" version))
+              (sha256
+               (base32
+                "0a0idq4y5frv7qsg2x62jd7rd272749xk4x99misf5rcifk2d7wi"))))
+    (build-system python-build-system)
+    (arguments
+     `(#:tests? #f)) ; no test suite
+    (synopsis "Snowball stemming library collection for Python")
+    (description "This package provides 16 stemmer algorithms generated from
+Snowball algorithms.")
+    (home-page "https://github.com/shibukawa/snowball_py")
+    (license bsd-2)))
+
+(define-public python2-snowballstemmer
+  (package-with-python2 python-snowballstemmer))