I encountered this when I added a unit test case that invoked os.chdir() with a temporary directory on Linux. After the directory was removed, some of the subsequent test cases failed, although I don’t think they should depend on a particular CWD.

I suspect the main problem might be code that is trying to dynamically import modules, and the interpreter is trying to search for modules in the current directory. I would expect it to happily go on to the other standard module directories or raise ImportError, just like if the current directory is valid but empty, or an nonexistent directory is in the module search path list.

Code to set up missing CWD:

import os
from tempfile import TemporaryDirectory
with TemporaryDirectory() as dir:
    os.chdir(dir)

Quick recovery:

os.chdir("/")

Examples of failures:

>>> "\N{COPYRIGHT SIGN}"
  File "<stdin>", line 1
SyntaxError: (unicode error) \N escapes not supported (can't load unicodedata module)
>>> datetime.strptime("", "")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<frozen importlib._bootstrap>", line 2237, in _find_and_load
  File "<frozen importlib._bootstrap>", line 2222, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 2164, in _find_spec
  File "<frozen importlib._bootstrap>", line 1940, in find_spec
  File "<frozen importlib._bootstrap>", line 1911, in _get_spec
  File "<frozen importlib._bootstrap>", line 1879, in _path_importer_cache
FileNotFoundError: [Errno 2] No such file or directory
>>> HTTPConnection("localhost").request("GET", "/")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.4/http/client.py", line 1090, in request
    self._send_request(method, url, body, headers)
  File "/usr/lib/python3.4/http/client.py", line 1128, in _send_request
    self.endheaders(body)
  File "/usr/lib/python3.4/http/client.py", line 1086, in endheaders
    self._send_output(message_body)
  File "/usr/lib/python3.4/http/client.py", line 924, in _send_output
    self.send(msg)
  File "/usr/lib/python3.4/http/client.py", line 859, in send
    self.connect()
  File "/usr/lib/python3.4/http/client.py", line 836, in connect
    self.timeout, self.source_address)
  File "/usr/lib/python3.4/socket.py", line 491, in create_connection
    for res in getaddrinfo(host, port, 0, SOCK_STREAM):
  File "/usr/lib/python3.4/socket.py", line 530, in getaddrinfo
    for res in _socket.getaddrinfo(host, port, family, type, proto, flags):
  File "/usr/lib/python3.4/encodings/__init__.py", line 98, in search_function
    level=0)
  File "/usr/lib/python3.4/encodings/idna.py", line 3, in <module>
    import stringprep, re, codecs
  File "<frozen importlib._bootstrap>", line 2237, in _find_and_load
  File "<frozen importlib._bootstrap>", line 2222, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 2164, in _find_spec
  File "<frozen importlib._bootstrap>", line 1940, in find_spec
  File "<frozen importlib._bootstrap>", line 1911, in _get_spec
  File "<frozen importlib._bootstrap>", line 1879, in _path_importer_cache
FileNotFoundError: [Errno 2] No such file or directory

>>> from datetime import datetime
>>> from http.client import HTTPConnection
These two also generate the FileNotFoundError

My workaround is to add this to my test case:
self.addCleanup(os.chdir, os.getcwd())