Add a comment on how to fix pyasn1's definition of ResponderID.

Change-Id: Id17b44c1ea5a3ccdb726c9495b8b6e66e2bc46b7
Reviewed-on: https://chromium-review.googlesource.com/685540Reviewed-by: Steven Valdez <svaldez@chromium.org>
Commit-Queue: Eric Roman <eroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#504476}

net/data/ocsp_unittest/make_ocsp.py

@@ -339,6 +339,13 @@ Store(
     'Uses byName to identify the signer',
     CA,
     Create(responder=GetName(CA)))
+
+# TODO(eroman): pyasn1 module has a bug in rfc2560.ResponderID() that will use
+# IMPLICIT rather than EXPLICIT tagging for byKey
+# (https://github.com/etingof/pyasn1-modules/issues/8). If using an affected
+# version of the library you will need to patch pyasn1_modules/rfc2560.py and
+# replace "implicitTag" with "explicitTag" in ResponderID to generate this
+# test data correctly.
 Store(
     'responder_id',
     'Uses byKey to identify the signer',