gh-37178: `sage.features.threejs`: Fix modularization regression after #37024
    
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`sage.features` is shipped by **sagemath-environment**, but the version
file that the Feature introduced in #37024 uses is shipped by
**sagemath-repl**.

This breaks doctesting in a modularized environment. As seen in
ipython/ipython#14317 (https://github.com/ipytho
n/ipython/actions/runs/7731330166/job/21078723213?pr=14317#step:9:136)


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URL: #37178
Reported by: Matthias Köppe
Reviewer(s): Gonzalo Tornaría, Kwankyu Lee, Matthias Köppe

Author: Release Manager

src/sage/features/threejs.py

@@ -25,18 +25,22 @@ def __init__(self):
         """
         from sage.env import SAGE_SHARE, THREEJS_DIR
 
-        version = self.required_version()
-
         threejs_search_path = THREEJS_DIR or (
             os.path.join(SAGE_SHARE, "jupyter", "nbextensions", "threejs-sage"),
             os.path.join(SAGE_SHARE, "sagemath", "threejs-sage"),
             os.path.join(SAGE_SHARE, "sage", "threejs"),
             os.path.join(SAGE_SHARE, "threejs-sage")
             )
 
+        try:
+            version = self.required_version()
+            filename = os.path.join(version, "three.min.js")
+        except FileNotFoundError:
+            filename = 'unknown'
+
         StaticFile.__init__(
             self, name="threejs",
-            filename=os.path.join(version, "three.min.js"),
+            filename=filename,
             spkg="threejs",
             type="standard",
             search_path=threejs_search_path,
@@ -46,6 +50,11 @@ def required_version(self):
         """
         Return the version of threejs that Sage requires.
 
+        Defining what version is required is delegated to the distribution package
+        that provides the file ``threejs-version.txt`` in :mod:`sage.ext_data.threejs`.
+
+        If the file is not provided, :class:`FileNotFoundError` is raised.
+
         EXAMPLES::
 
             sage: from sage.features.threejs import Threejs