/usr/share/igtf-policy/classic/DigiCertGridCA-1G2-Classic-2015.namespaces is in igtf-policy-classic 1.88-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17  | ##############################################################################
#NAMESPACES-VERSION: 1.0
#
# @(#)62c4a178.namespaces
# CA alias    : DigiCertGridCA-1-G2-Classic-2015
#    subord_of: DigiCertGridRootCA-Root
#    subjectDN: /DC=com/DC=DigiCert-Grid/O=DigiCert Grid/CN=DigiCert Grid CA-1 G2
#    hash     : 62c4a178
TO Issuer "/DC=com/DC=DigiCert-Grid/O=DigiCert Grid/CN=DigiCert Grid CA-1 G2" \
  PERMIT Subject "/DC=com/DC=DigiCert-Grid/.*"
TO Issuer "/DC=com/DC=DigiCert-Grid/O=DigiCert Grid/CN=DigiCert Grid CA-1 G2" \
  PERMIT Subject "/DC=com/DC=DigiCertGrid/.*"
TO Issuer "/DC=com/DC=DigiCert-Grid/O=DigiCert Grid/CN=DigiCert Grid CA-1 G2" \
  PERMIT Subject "/C=US/O=DigiCert Grid/.*"
 |