Bug#940679: pandas: random test crashes

[Rebecca N. Palmer]

Control: tags -1 unreproducible

Running just the affected test files (in installed -6) produced no 
failures in ~350 attempts.  The build of -7 succeeded on amd64; it 
failed on ppc64, but as the log isn't available yet, I don't know if 
it's this bug.

While both tests involve time-related dtypes, the test data is a fixed 
set not the current time, so the time of build probably isn't what 
decides which runs fail.

Does anyone have a reproducible way to trigger this error?