tests: improve search of a free TCP port (#72645)

hobo/test_utils.py

@@ -16,6 +16,9 @@
 
 import hashlib
 import os
+import socket
+import struct
+from contextlib import closing
 
 
 def get_safe_db_name(max_length=53):
@@ -47,3 +50,12 @@ def get_safe_db_name(max_length=53):
     truncated_db_name = full_db_name[:prefix_length] + '_' + hashcode + '_' + full_db_name[-suffix_length:]
     assert len(truncated_db_name) == max_length
     return truncated_db_name
+
+
+def find_free_port():
+    with closing(socket.socket(socket.AF_INET, socket.SOCK_STREAM)) as s:
+        s.bind(('', 0))
+        # SO_LINGER (man 7 socket) l_onoff=1 l_linger=0, immediately release
+        # the port on closing of the socket
+        s.setsockopt(socket.SOL_SOCKET, socket.SO_LINGER, struct.pack("ii", 1, 0))
+        return s.getsockname()[1]

tests/test_emails.py

@@ -16,17 +16,12 @@ from test_manager import login
 
 from hobo.emails.validators import validate_email_address
 from hobo.environment.models import Variable
+from hobo.test_utils import find_free_port
 
 
 @pytest.fixture
 def port_available():
-    errno = 0
-    while not errno:
-        port = random.randint(49152, 65534)
-        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
-        errno = sock.connect_ex(('127.0.0.1', port))
-        sock.close()
-    return port
+    return find_free_port()
 
 
 @pytest.fixture