Support for IBM Z missing

[rdapp1]

When trying to run a benchmark I noticed that the function collect_cpu_freq() in _collect_metadata.py parses the output of /proc/cpuinfo but fails on the IBM Z (mainframe, S/390).

On Linux on IBM Z the output may look like this:

vendor_id       : IBM/S390
# processors    : 16
[...]
processor 0: version = 00,  identification = [...]
cpu number      : 0
cpu MHz dynamic : 5208
cpu MHz static  : 5208
[...]

The code splits lines starting with processor at ':' which will not yield a proper CPU number on Z. It should suffice, however, to check the vendor_id for IBM/S390 and look for cpu number in this case instead. The parsing of of the frequency should work ok with the existing logic.

[vstinner]

Do you want to work on a patch?

[rdapp1]

No idea why the email response to this thread did not go through, here it is again:

Unfortunately, it would take me a while to obtain copyright assignment
for a new project :( I already have a fix on my machine that is rather
trivial and works as far as I can tell, I just cannot post it here for
legal reasons. Therefore, I assume it will be faster if you fix it.

[vstinner]

Fixed by commit 7febee0 which will be in the 1.6 release that I will release shortly.