💅 Address all instances of BytesWarning

Things like byte-to-int comparisons and interpolation of bytes into
str were present in the code base. This patch fixes that by making
sure that the variables are always of compatible types in these cases.

cheroot/server.py

@@ -209,7 +209,11 @@ def __call__(self, rfile, hdict=None):  # noqa: C901  # FIXME
             if not line.endswith(CRLF):
                 raise ValueError('HTTP requires CRLF terminators')
 
-            if line[0] in (SPACE, TAB):
+            if line[:1] in (SPACE, TAB):
+                # NOTE: `type(line[0]) is int` and `type(line[:1]) is bytes`.
+                # NOTE: The former causes a the following warning:
+                # NOTE: `BytesWarning('Comparison between bytes and int')`
+                # NOTE: The latter is equivalent and does not.
                 # It's a continuation line.
                 v = line.strip()
             else:

cheroot/test/test_conn.py

@@ -53,7 +53,8 @@ def upload(req, resp):
                 "'POST' != request.method %r" %
                 req.environ['REQUEST_METHOD'],
             )
-        return "thanks for '%s'" % req.environ['wsgi.input'].read()
+        input_contents = req.environ['wsgi.input'].read().decode('utf-8')
+        return f"thanks for '{input_contents !s}'"
 
     def custom_204(req, resp):
         """Render response with status 204."""
@@ -917,7 +918,7 @@ def test_100_Continue(test_client):
     status_line, _actual_headers, actual_resp_body = webtest.shb(response)
     actual_status = int(status_line[:3])
     assert actual_status == 200
-    expected_resp_body = ("thanks for '%s'" % body).encode()
+    expected_resp_body = f"thanks for '{body.decode() !s}'".encode()
     assert actual_resp_body == expected_resp_body
     conn.close()
 
@@ -987,7 +988,7 @@ def test_readall_or_close(test_client, max_request_body_size):
     status_line, actual_headers, actual_resp_body = webtest.shb(response)
     actual_status = int(status_line[:3])
     assert actual_status == 200
-    expected_resp_body = ("thanks for '%s'" % body).encode()
+    expected_resp_body = f"thanks for '{body.decode() !s}'".encode()
     assert actual_resp_body == expected_resp_body
     conn.close()