Ensure that file exists before copying for local build.

Author: vpratz

sphinx_polyversion/driver.py

@@ -342,7 +342,7 @@ async def build_local(self) -> None:
                     source = self.root / filename
                     target = path / filename
                     target.parent.mkdir(parents=True, exist_ok=True)
-                    if not target.exists():
+                    if source.exists() and not target.exists():
                         shutil.copy2(source, target, follow_symlinks=False)
 
                 # as .git is not copied, we have to initialize a dummy git repository