set http prefix in python geq 3.7.6

Signed-off-by: George Mossessian <gmossessian@gmail.com>

prometheus_client/exposition.py

@@ -29,7 +29,8 @@
 """Content type of the latest text format"""
 
 PYTHON26_OR_OLDER = sys.version_info < (2, 7)
-
+# Due to https://bugs.python.org/issue27657:
+PYTHON376_OR_NEWER = sys.version_info > (3, 7, 5)
 
 def make_wsgi_app(registry=REGISTRY):
     """Create a WSGI app which serves the metrics from a registry."""
@@ -341,7 +342,10 @@ def delete_from_gateway(
 
 def _use_gateway(method, gateway, job, registry, grouping_key, timeout, handler):
     gateway_url = urlparse(gateway)
-    if not gateway_url.scheme or (PYTHON26_OR_OLDER and gateway_url.scheme not in ['http', 'https']):
+    if not gateway_url.scheme or (
+            (PYTHON376_OR_NEWER or PYTHON26_OR_OLDER)
+            and gateway_url.scheme not in ['http', 'https']
+    ):
         gateway = 'http://{0}'.format(gateway)
     url = '{0}/metrics/{1}/{2}'.format(gateway, *_escape_grouping_key("job", job))
 

tests/test_exposition.py

@@ -235,6 +235,13 @@ def test_push(self):
         self.assertEqual(self.requests[0][0].headers.get('content-type'), CONTENT_TYPE_LATEST)
         self.assertEqual(self.requests[0][1], b'# HELP g help\n# TYPE g gauge\ng 0.0\n')
 
+    def test_push_schemeless_url(self):
+        push_to_gateway(self.address.replace('http://', ''), "my_job", self.registry)
+        self.assertEqual(self.requests[0][0].command, 'PUT')
+        self.assertEqual(self.requests[0][0].path, '/metrics/job/my_job')
+        self.assertEqual(self.requests[0][0].headers.get('content-type'), CONTENT_TYPE_LATEST)
+        self.assertEqual(self.requests[0][1], b'# HELP g help\n# TYPE g gauge\ng 0.0\n')
+
     def test_push_with_groupingkey(self):
         push_to_gateway(self.address, "my_job", self.registry, {'a': 9})
         self.assertEqual(self.requests[0][0].command, 'PUT')