[requests] add Deprecation Warning for client attributes

Author: Emanuele Palazzetti

ddtrace/contrib/requests/legacy.py

@@ -1,11 +1,31 @@
+# [Deprecation]: this module contains deprecated functions
+# that will be removed in newer versions of the Tracer.
 from ddtrace import config
 
+from ...utils.deprecation import deprecation
+
 
 def _distributed_tracing(self):
-    """Backward compatibility"""
+    """Deprecated: this method has been deprecated in favor of
+    the configuration system. It will be removed in newer versions
+    of the Tracer.
+    """
+    deprecation(
+        name='client.distributed_tracing',
+        message='Use the configuration object instead `config.get_from(client)[\'distributed_tracing\'`',
+        version='1.0.0',
+    )
     return config.get_from(self)['distributed_tracing']
 
 
 def _distributed_tracing_setter(self, value):
-    """Backward compatibility"""
+    """Deprecated: this method has been deprecated in favor of
+    the configuration system. It will be removed in newer versions
+    of the Tracer.
+    """
+    deprecation(
+        name='client.distributed_tracing',
+        message='Use the configuration object instead `config.get_from(client)[\'distributed_tracing\'] = value`',
+        version='1.0.0',
+    )
     config.get_from(self)['distributed_tracing'] = value