gnu: Add python-contextvars.

* gnu/packages/python-xyz.scm (python-contextvars): New variable.

Signed-off-by: Leo Famulari <leo@famulari.name>

gnu/packages/python-xyz.scm

@@ -23223,3 +23223,24 @@ (define-public python2-gamera
      "Gamera is a toolkit for building document image recognition systems.")
     (home-page "https://gamera.informatik.hsnr.de/")
     (license license:gpl2+)))
+
+(define-public python-contextvars
+  (package
+    (name "python-contextvars")
+    (version "2.4")
+    (source
+      (origin
+        (method url-fetch)
+        (uri (pypi-uri "contextvars" version))
+        (sha256
+          (base32
+            "17n3w8c20kgkgc6khaafdhhlcdj4bzman4paxqsl7harma59137k"))))
+    (build-system python-build-system)
+    (propagated-inputs
+      `(("python-immutables" ,python-immutables)))
+    (home-page
+      "https://github.com/MagicStack/contextvars")
+    (synopsis "PEP 567 Backport")
+    (description "This package implements a backport of Python 3.7
+@code{contextvars} module (see PEP 567) for Python 3.6.")
+    (license license:asl2.0)))