gnu: Add python-linecache2.

* gnu/packages/python.scm (python-linecache2, python2-linecache2): New
  variables.

gnu/packages/python.scm

@@ -16503,3 +16503,32 @@ (define-public python-twine
 
 (define-public python2-twine
   (package-with-python2 python-twine))
+
+(define-public python-linecache2
+  (package
+    (name "python-linecache2")
+    (version "1.0.0")
+    (source
+      (origin
+        (method url-fetch)
+        (uri (pypi-uri "linecache2" version))
+        (sha256
+          (base32
+            "0z79g3ds5wk2lvnqw0y2jpakjf32h95bd9zmnvp7dnqhf57gy9jb"))))
+    (build-system python-build-system)
+    (arguments
+     `(;; The tests depend on unittest2, and our version is a bit too old.
+       #:tests? #f))
+    (native-inputs
+     `(("python-pbr" ,python-pbr)))
+    (home-page
+      "https://github.com/testing-cabal/linecache2")
+    (synopsis "Backports of the linecache module")
+    (description
+      "The linecache module allows one to get any line from any file, while
+attempting to optimize internally, using a cache, the common case where many
+lines are read from a single file.")
+    (license license:psfl)))
+
+(define-public python2-linecache2
+  (package-with-python2 python-linecache2))