If a python script receives SIGINT while the interpreter is starting up,
it's possible to get the message "import site failed; use -v for
traceback" printed on standard error and for execution to proceed. It
also seems to be possible to get half-imported modules and for the
script to fail later claiming that something like "os.getenv" doesn't exist.

If I do as instructed and use -v for traceback I get something like:

'import site' failed; traceback:
Traceback (most recent call last):
  File "/usr/lib/python2.4/site.py", line 61, in ?
    import os
  File "/usr/lib/python2.4/os.py", line 683, in ?
    import copy_reg as _copy_reg
  File "/usr/lib/python2.4/copy_reg.py", line 5, in ?
    """
KeyboardInterrupt 

I imagine there exists some code like
try:
    import site
except:
    sys.stderr.write("import site failed; use -v for traceback\n")

though I couldn't find any. If so, it seems clear that KeyboardInterrupt
needs to be re-raised, or Python's special handler for SIGINT installed
rather later.