fix: ensure temp dir available (#15195)

## Description

We add handling for cases where a temporary directory is not available.

Fixes #15166.

Author: P403n1x87

ddtrace/internal/ipc.py

@@ -93,14 +93,17 @@ def open_file(path, mode):
         return unpatched_open(fd, mode)
 
 
-TMPDIR = Path(tempfile.gettempdir())
+try:
+    TMPDIR: typing.Optional[Path] = Path(tempfile.gettempdir())
+except FileNotFoundError:
+    TMPDIR = None
 
 
 class SharedStringFile:
     """A simple shared-file implementation for multiprocess communication."""
 
     def __init__(self) -> None:
-        self.filename: typing.Optional[str] = str(TMPDIR / secrets.token_hex(8))
+        self.filename: typing.Optional[str] = str(TMPDIR / secrets.token_hex(8)) if TMPDIR is not None else None
 
     def put(self, data: str) -> None:
         """Put a string into the file."""

releasenotes/notes/fix-ipc-valid-tmp-dir-063d8abcc1835747.yaml

@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    Prevent startup failure when a temporary directory is not available.