make sure all examples work on python 3

fix #1961

examples/echo.py

@@ -24,8 +24,7 @@ def app(environ, start_response):
     response_headers = [
         ('Content-type', 'text/plain'),
         ('Content-Length', str(len(data))),
-        ('X-Gunicorn-Version', __version__),
-        ("Test", "test тест"),
+        ('X-Gunicorn-Version', __version__)
     ]
     start_response(status, response_headers)
     return iter([data])

examples/log_app.py

@@ -13,4 +13,4 @@ def app(environ, start_response):
     log.info("Hello Info!")
     log.warn("Hello Warn!")
     log.error("Hello Error!")
-    return ["Hello World!\n"]
+    return [b"Hello World!\n"]

examples/readline_app.py

@@ -9,7 +9,7 @@
 #
 # Launch a server with the app in a terminal
 #
-#     $ gunicorn -w3 readline:app
+#     $ gunicorn -w3 readline_app:app
 #
 # Then in another terminal launch the following command:
 #
@@ -27,8 +27,7 @@ def app(environ, start_response):
     response_headers = [
         ('Content-type', 'text/plain'),
         ('Transfer-Encoding', "chunked"),
-        ('X-Gunicorn-Version', __version__),
-        #("Test", "test тест"),
+        ('X-Gunicorn-Version', __version__)
     ]
     start_response(status, response_headers)
 
@@ -42,4 +41,4 @@ def app(environ, start_response):
         print(line)
         lines.append(line)
 
-    return iter(lines)
+    return iter(lines)

examples/test.py

@@ -20,8 +20,7 @@ def app(environ, start_response):
     response_headers = [
         ('Content-type', 'text/plain'),
         ('Content-Length', str(len(data))),
-        ('X-Gunicorn-Version', __version__),
-        #("Test", "test тест"),
+        ('X-Gunicorn-Version', __version__)
     ]
     start_response(status, response_headers)
     return iter([data])