avocado.utils.process: Add method to check whether sudo is configured

The `avocado.utils.process` allows the use of sudo, but it might not be
always enabled/configured in the system. This method should allow
detecting whether it is or is not available.
Signed-off-by: NLukáš Doktor <ldoktor@redhat.com>

avocado/utils/process.py

@@ -98,6 +98,18 @@ class CmdError(Exception):
             return "CmdError"
 
 
+def can_sudo():
+    """
+    :return: True when sudo is available (or is root)
+    """
+    if os.getuid() == 0:
+        return True
+    elif system_output("id -u", ignore_status=True, sudo=True).strip() == "0":
+        return True
+    else:
+        return False
+
+
 def pid_exists(pid):
     """
     Return True if a given PID exists.