imgmath: Make lockfile optional

Author: jschueller

pyproject.toml

@@ -84,7 +84,6 @@ dependencies = [
     "roman-numerals-py>=1.0.0",
     "packaging>=23.0",
     "colorama>=0.4.6; sys_platform == 'win32'",
-    "filelock>=3.0",
 ]
 dynamic = ["version"]
 
@@ -108,6 +107,9 @@ lint = [
     "pypi-attestations==0.0.25",
     "betterproto==2.0.0b6",
 ]
+package = [
+"filelock>=3.0",
+]
 test = [
     "pytest>=8.0",
     "pytest-xdist[psutil]>=3.4",

sphinx/ext/imgmath.py

@@ -17,7 +17,6 @@
 from subprocess import CalledProcessError
 from typing import TYPE_CHECKING
 
-import filelock
 from docutils import nodes
 
 import sphinx
@@ -275,7 +274,12 @@ def render_math(
     lock: Any = contextlib.nullcontext()
     if self.builder.parallel_ok:
         lockfile = generated_path.with_suffix(generated_path.suffix + '.lock')
-        lock = filelock.FileLock(lockfile)
+        try:
+            import filelock  # type: ignore[import-not-found]
+
+            lock = filelock.FileLock(lockfile)
+        except ImportError:
+            pass
 
     with lock:
         if not generated_path.is_file():