On Solaris 11.3 (intel tested, but I assume issue is on SPARC as well),
I found the following fails:
  import os
  os.urandom(2500)

The above throws OSError: [Errno 22] Invalid argument.

It turns out that the Solaris version of getrandom() is limited to returning
no more than 1024 bytes, per the manpage:
  The getrandom() and getentropy() functions fail if:

  EINVAL    The flags are not set to GRND_RANDOM, GRND_NONBLOCK or  both,
            or bufsz is <= 0 or > 1024.

I've attached a possible patch for this issue, against the 3.5.1 source
tree.