support/testing: set date in emulated machine

When time comes to check certificates, the date and time in the emulated
machine should be close enough to the actual values, so that certificate
validity can be checked.

Some Qemu machines have an RTC (e.g. arm vexpress-a9 has a pl031), and
the kernel needs a driver for those RTC. It is not guaranteed that the
machine used for a test meets those two conditions; in such a case, the
time in the machine starts way back in the past (1970-01-01T00:00:00Z on
sysv, or the release date of systemd). This is the case with the default
kernel, so such tests do not have the proper time.

Set the date to the date of the host system. This is going to be accurate
to the second, which is, by far, enough for our purpose.

To avoid having to consider what combination of emulated machine and kernel
configuration are being used, we always set the date, as this is a
generic step that should be done by the infra (like login in as root is).

The Emulator() class doesn't inherit from unittest.TestCase, so we can't
call any of the usual self.assertXXX() methods; instead, we just raise
a standard exception, like is done a few lines above to detect the login
prompt.

Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Cc: Ricardo Martincoski <ricardo.martincoski@datacom.com.br>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Julien Olivain <ju.o@free.fr>

support/testing/infra/emulator.py

@@ -5,6 +5,7 @@ import os
 
 import pexpect
 import pexpect.replwrap
+import time
 
 import infra
 
@@ -152,6 +153,10 @@ class Emulator(object):
 
         self.connect_shell()
 
+        output, exit_code = self.run(f"date @{int(time.time())}")
+        if exit_code:
+            raise SystemError("Cannot set date in virtual machine")
+
     def connect_shell(self):
         extra_init_cmd = " && ".join([
             'export PAGER=cat',