py3: remove imports from utils.compat

tests/utils/httpd.py

@@ -1,14 +1,7 @@
 import hashlib
 import os
 import threading
-
-# Moved in Python 2 -> 3, used only here.
-# Not adding to dvc.utils.compat to not load http.server for non-test runs.
-try:
-    from http.server import HTTPServer
-except ImportError:
-    from BaseHTTPServer import HTTPServer
-
+from http.server import HTTPServer
 from RangeHTTPServer import RangeRequestHandler