Remove support for Python 2 and 3.5

- Upgrades syntax to Python 3.6+ with f-strings
- Removes most usage of six
- Removes documentation relevant to Python 2
- Removes universal wheel config
- Removes mock dependency for testing

1 files changed, 1 insertions, 1 deletions

diff --git a/dummyserver/proxy.py b/dummyserver/proxy.py
index 0cd8dedd..3cb974c0 100755
--- a/dummyserver/proxy.py
+++ b/dummyserver/proxy.py
@@ -143,5 +143,5 @@ if __name__ == "__main__":
     if len(sys.argv) > 1:
         port = int(sys.argv[1])
 
-    print("Starting HTTP proxy on port %d" % port)
+    print(f"Starting HTTP proxy on port {port}")
     run_proxy(port)