Make the output reproducible

Whilst working on the Reproducible Builds effort [0] I noticed that
sphinx-panels and sphinx-design do not create reproducible output.

This is because it uses Python's uuid.uuid4 to generate unique identifiers, but
those numbers are random/nondeterminstic by design. This patch will seed these
random numbers from SOURCE_DATE_EPOCH if it exists, otherwise it will revert
back to random numbers.

I originally filed this in Debian as bug #1017475 [1], as well as within
sphinx-panels [2]

 [0] https://reproducible-builds.org/
 [1] https://bugs.debian.org/1017475
 [2] executablebooks/sphinx-panels#82

Author: lamby

sphinx_design/tabs.py

@@ -1,5 +1,9 @@
+import os
+import random
+import time
+import uuid
+
 from typing import List
-from uuid import uuid4
 
 from docutils import nodes
 from docutils.parsers.rst import directives
@@ -12,6 +16,9 @@
 
 LOGGER = getLogger(__name__)
 
+rnd = random.Random()
+rnd.seed(os.environ.get("SOURCE_DATE_EPOCH", time.time()))
+
 
 def setup_tabs(app: Sphinx) -> None:
     app.add_directive("tab-set", TabSetDirective)
@@ -209,7 +216,7 @@ class TabSetHtmlTransform(SphinxPostTransform):
     formats = ("html",)
 
     def get_unique_key(self):
-        return str(uuid4())
+        return uuid.UUID(int=rnd.getrandbits(128), version=4).hex
 
     def run(self) -> None:
         """Run the transform."""