emacs 27.1 FTBFS in hirsute because of new unit tests requiring DNS lookup

The new unit tests fail consistently on all supported architectures:

Running 18 tests (2021-01-11 18:38:54+0000, selector `(not (or (tag :expensive-test) (tag :unstable)))')
google.com/0 Name or service not known
Test lookup-family-specification backtrace:
  signal(ert-test-failed (((should (network-lookup-address-info "googl
  ert-fail(((should (network-lookup-address-info "google.com" 'ipv4))
  #f(compiled-function () #<bytecode 0x158e7f7a0075>)()
  ert--run-test-internal(#s(ert--test-execution-info :test #s(ert-test
  ert-run-test(#s(ert-test :name lookup-family-specification :document
  ert-run-or-rerun-test(#s(ert--stats :selector (not ...) :tests [...
  ert-run-tests((not (or (tag :expensive-test) (tag :unstable))) #f(co
  ert-run-tests-batch((not (or (tag :expensive-test) (tag :unstable)))
  ert-run-tests-batch-and-exit((not (or (tag :expensive-test) (tag :un
  eval((ert-run-tests-batch-and-exit '(not (or (tag :expensive-test) (
  command-line-1(("-L" ":/<<BUILDDIR>>/emacs-27.1+1/debian/build
  command-line()
  normal-top-level()
Test lookup-family-specification condition:
    (ert-test-failed
     ((should
       (network-lookup-address-info "google.com" 'ipv4))
      :form
      (network-lookup-address-info "google.com" ipv4)
      :value nil))
   FAILED 1/18 lookup-family-specification (0.001748 sec)
google.com/0 Name or service not known
google.com/0 Name or service not known
Test lookup-google backtrace:
  signal(ert-test-failed (((should addresses-both) :form addresses-bot
  ert-fail(((should addresses-both) :form addresses-both :value nil))
  #f(compiled-function () #<bytecode 0x158e7f7a1391>)()
  ert--run-test-internal(#s(ert--test-execution-info :test #s(ert-test
  ert-run-test(#s(ert-test :name lookup-google :documentation "Check t
  ert-run-or-rerun-test(#s(ert--stats :selector (not ...) :tests [...
  ert-run-tests((not (or (tag :expensive-test) (tag :unstable))) #f(co
  ert-run-tests-batch((not (or (tag :expensive-test) (tag :unstable)))
  ert-run-tests-batch-and-exit((not (or (tag :expensive-test) (tag :un
  eval((ert-run-tests-batch-and-exit '(not (or (tag :expensive-test) (
  command-line-1(("-L" ":/<<BUILDDIR>>/emacs-27.1+1/debian/build
  command-line()
  normal-top-level()
Test lookup-google condition:
    (ert-test-failed
     ((should addresses-both)
      :form addresses-both :value nil))
   FAILED 2/18 lookup-google (0.001174 sec)
xn--fa-hia.de/0 Name or service not known
Test lookup-unicode-domains backtrace:
  signal(ert-test-failed (((should (network-lookup-address-info (puny-
  ert-fail(((should (network-lookup-address-info (puny-encode-domain "
  #f(compiled-function () #<bytecode 0x158e7f7a0171>)()
  ert--run-test-internal(#s(ert--test-execution-info :test #s(ert-test
  ert-run-test(#s(ert-test :name lookup-unicode-domains :documentation
  ert-run-or-rerun-test(#s(ert--stats :selector (not ...) :tests [...
  ert-run-tests((not (or (tag :expensive-test) (tag :unstable))) #f(co
  ert-run-tests-batch((not (or (tag :expensive-test) (tag :unstable)))
  ert-run-tests-batch-and-exit((not (or (tag :expensive-test) (tag :un
  eval((ert-run-tests-batch-and-exit '(not (or (tag :expensive-test) (
  command-line-1(("-L" ":/<<BUILDDIR>>/emacs-27.1+1/debian/build
  command-line()
  normal-top-level()
Test lookup-unicode-domains condition:
    (ert-test-failed
     ((should
       (network-lookup-address-info
 (puny-encode-domain "faß.de")))
      :form
      (network-lookup-address-info "xn--fa-hia.de")
      :value nil))
   FAILED 3/18 lookup-unicode-domains (0.008471 sec)
  skipped 4/18 make-process-w32-debug-spawn-error (0.000130 sec)
   passed 5/18 make-process/file-handler/disable (0.001022 sec)
   passed 6/18 make-process/file-handler/found (0.000069 sec)
   passed 7/18 make-process/file-handler/not-found (0.000675 sec)
   passed 8/18 make-process/mix-stderr (0.001617 sec)
   passed 9/18 make-process/noquery-stderr (0.000495 sec)
   passed 10/18 make-process/stop (0.000100 sec)
emacs.invalid/0 Temporary failure in name resolution
   passed 11/18 non-existent-lookup-failure (0.005292 sec)
   passed 12/18 process-test-sentinel-accept-process-output (0.001499 sec)
   passed 13/18 process-test-sentinel-sit-for (0.010669 sec)
   passed 14/18 process-test-stderr-buffer (0.001318 sec)
   passed 15/18 process-test-stderr-filter (0.001192 sec)
   passed 16/18 set-process-filter-t (1.030961 sec)
   passed 17/18 start-process-should-not-modify-arguments (0.001024 sec)
google.com/0 Name or service not known
Test unibyte-domain-name backtrace:
  signal(ert-test-failed (((should (network-lookup-address-info (strin
  ert-fail(((should (network-lookup-address-info (string-to-unibyte "g
  #f(compiled-function () #<bytecode 0x158e7f7a0211>)()
  ert--run-test-internal(#s(ert--test-execution-info :test #s(ert-test
  ert-run-test(#s(ert-test :name unibyte-domain-name :documentation "U
  ert-run-or-rerun-test(#s(ert--stats :selector ... :tests ... :test-m
  ert-run-tests((not (or (tag :expensive-test) (tag :unstable))) #f(co
  ert-run-tests-batch((not (or (tag :expensive-test) (tag :unstable)))
  ert-run-tests-batch-and-exit((not (or (tag :expensive-test) (tag :un
  eval((ert-run-tests-batch-and-exit '(not (or (tag :expensive-test) (
  command-line-1(("-L" ":/<<BUILDDIR>>/emacs-27.1+1/debian/build
  command-line()
  normal-top-level()
Test unibyte-domain-name condition:
    (ert-test-failed
     ((should
       (network-lookup-address-info
 (string-to-unibyte "google.com")))
      :form
      (network-lookup-address-info "google.com")
      :value nil))
   FAILED 18/18 unibyte-domain-name (0.000899 sec)

Ran 18 tests, 13 results as expected, 4 unexpected, 1 skipped (2021-01-11 18:38:55+0000, 1.385232 sec)

4 unexpected results:
   FAILED lookup-family-specification
   FAILED lookup-google
   FAILED lookup-unicode-domains
   FAILED unibyte-domain-name