scm: Close stdin of processing command

It is possible the user set a command to run in cloned Git repository,
but that command can ask for additional input. However Pungi will
capture all output, so if there is a prompt, it will never be shown.

In order to prevent confusion ("Did this hang?"), let's send empty
string to stdin of the program. That will cause any possible read to see
EOF immediately, which should cause an error that will then be reported
by Pungi to the user.

It is still possible the program will wait for input if it reads
directly from TTY. However in such case the prompt should hopefully also
be sent to TTY directly, so that possible confusion should be cleared.

JIRA: COMPOSE-3598
Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>

pungi/wrappers/scm.py

@@ -44,7 +44,13 @@ class ScmBase(kobo.log.LoggingBase):
     def run_process_command(self, cwd):
         if self.command:
             self.log_debug('Running "%s"' % self.command)
-            retcode, output = run(self.command, workdir=cwd, can_fail=True)
+            retcode, output = run(
+                self.command,
+                workdir=cwd,
+                can_fail=True,
+                stdin_data="",
+                universal_newlines=True,
+            )
             if retcode != 0:
                 self.log_error('Output was: %r' % output)
                 raise RuntimeError('%r failed with exit code %s'