Update virtualenv from 16.4.3 to 16.5.0 (#11245)

requirements/travis_base.txt

@@ -12,9 +12,9 @@ tox==3.9.0 \
     --hash=sha256:665cbdd99f5c196dd80d1d8db8c8cf5d48b1ae1f778bccd1bdf14d5aaf4ca0fc
 
 # Dependencies of Tox
-virtualenv==16.4.3 \
-    --hash=sha256:6aebaf4dd2568a0094225ebbca987859e369e3e5c22dc7d52e5406d504890417 \
-    --hash=sha256:984d7e607b0a5d1329425dd8845bd971b957424b5ba664729fab51ab8c11bc39
+virtualenv==16.5.0 \
+    --hash=sha256:15ee248d13e4001a691d9583948ad3947bcb8a289775102e4c4aa98a8b7a6d73 \
+    --hash=sha256:bfc98bb9b42a3029ee41b96dc00a34c2f254cbf7716bec824477b2c82741a5c4
 six==1.12.0 \
     --hash=sha256:3350809f0555b11f552448330d0b52d5f24c91a322ea4a15ef22629740f3761c \
     --hash=sha256:d16a0141ec1a18405cd4ce8b4613101da75da0e9a7aec5bdd4fa804d0e0eba73