EOFError: marshal data too short -- causes?

Tue Dec 29 01:50:55 EST 2015

Here's a sanatized stack trace off my web server:
 File ".../cgihelpers.py", line 10, in
 import cgitb
 File ".../py34/lib/python3.4/cgitb.py", line 24, in
 import inspect
 File ".../py34/lib/python3.4/inspect.py", line 54, in
 from dis import COMPILER_FLAG_NAMES as _flag_names
 File "", line 2237, in _find_and_load
 File "", line 2226, in _find_and_load_unlocked
 File "", line 1200, in _load_unlocked
 File "", line 1129, in _exec
 File "", line 1467, in exec_module
 File "", line 1570, in get_code
 File "", line 656, in _compile_bytecode
EOFError: marshal data too short
It worked this morning, and does this now. I hadn't changed anything.
The only reference I find on Google seems to be related to 
out-of-disk-space, so I cleaned up some files, but I'm not sure of how 
the web server mounts things; df didn't show particularly high usage in 
any of the disks it reported on.
The files I cleaned up are ever-growing log files that I need to clean 
up now and then manually, but cleaning them up didn't help... and df 
wasn't complaining anyway. So maybe out-of-disk-space is a red herring, 
or only one cause of this symptom.
When I log in to the web server with Putty, I can run Python at the 
command prompt, and "import dis" suffices to reproduce the problem.
Are there other causes of this symptom than out-of-disk-space? If it is 
out-of-disk-space, how could one determine which disk?
Maybe if not really out of space, it is a bad permission, disallowing 
creation of a temporary file? But how could one determine which 
temporary file, and where it would be written?