iotests: add file_path helper

Simple way to have auto generated filenames with auto cleanup. Like
FilePath but without using 'with' statement and without additional
indentation of the whole test.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20180312152126.286890-8-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: grammar tweak]
Signed-off-by: Eric Blake <eblake@redhat.com>

tests/qemu-iotests/iotests.py

@@ -27,6 +27,7 @@
 import json
 import signal
 import logging
+import atexit
 
 sys.path.append(os.path.join(os.path.dirname(__file__), '..', '..', 'scripts'))
 import qtest
@@ -250,6 +251,37 @@ def __exit__(self, exc_type, exc_val, exc_tb):
         return False
 
 
+def file_path_remover():
+    for path in reversed(file_path_remover.paths):
+        try:
+            os.remove(path)
+        except OSError:
+            pass
+
+
+def file_path(*names):
+    ''' Another way to get auto-generated filename that cleans itself up.
+
+    Use is as simple as:
+
+    img_a, img_b = file_path('a.img', 'b.img')
+    sock = file_path('socket')
+    '''
+
+    if not hasattr(file_path_remover, 'paths'):
+        file_path_remover.paths = []
+        atexit.register(file_path_remover)
+
+    paths = []
+    for name in names:
+        filename = '{0}-{1}'.format(os.getpid(), name)
+        path = os.path.join(test_dir, filename)
+        file_path_remover.paths.append(path)
+        paths.append(path)
+
+    return paths[0] if len(paths) == 1 else paths
+
+
 class VM(qtest.QEMUQtestMachine):
     '''A QEMU VM'''