Tests fail with GNU Emacs 27.1

Hi,
some tests (both at v0.7.0 and the current master) fail with GNU Emacs 27.1:
$ LANG=C.UTF-8 emacs -version
GNU Emacs 27.1
Copyright (C) 2020 Free Software Foundation, Inc.
GNU Emacs comes with ABSOLUTELY NO WARRANTY.
You may redistribute copies of GNU Emacs
under the terms of the GNU General Public License.
For more information about these matters, see the file named COPYING.

$ LANG=C.UTF-8 emacs -batch -Q -l package --eval "(add-to-list 'package-directory-list \"/usr/share/emacs/site-lisp/elpa\")" --eval "(add-to-list 'package-directory-list \"/usr/share/emacs/site-lisp/elpa-src\")" -f package-initialize -L . -L test --eval "(load \"undercover.el\")" -l test/first-example-library-test.el --eval \(ert-run-tests-batch-and-exit\)
Loading /tmp/undercover.el/undercover.el (source)...
Package cl is deprecated
Running 11 tests (2020-11-01 12:27:57+0500, selector ‘t’)
Test test-001/edebug-handlers-are-setted backtrace:
  signal(ert-test-failed (((should (eq 'undercover--stop-point-before 
  ert-fail(((should (eq 'undercover--stop-point-before (symbol-functio
  (if (unwind-protect (setq value-2 (apply fn-0 args-1)) (setq form-de
  (let (form-description-4) (if (unwind-protect (setq value-2 (apply f
  (let ((value-2 'ert-form-evaluation-aborted-3)) (let (form-descripti
  (let* ((fn-0 #'eq) (args-1 (condition-case err (let ((signal-hook-fu
  (closure (t) nil (let* ((fn-0 #'eq) (args-1 (condition-case err (let
  ert--run-test-internal(#s(ert--test-execution-info :test #s(ert-test
  ert-run-test(#s(ert-test :name test-001/edebug-handlers-are-setted :
  ert-run-or-rerun-test(#s(ert--stats :selector t :tests [#s(ert-test 
  ert-run-tests(t #f(compiled-function (event-type &rest event-args) #
  ert-run-tests-batch(nil)
  ert-run-tests-batch-and-exit()
  eval((ert-run-tests-batch-and-exit) t)
  command-line-1(("-l" "package" "--eval" "(add-to-list 'package-direc
  command-line()
  normal-top-level()
Test test-001/edebug-handlers-are-setted condition:
    (ert-test-failed
     ((should
       (eq 'undercover--stop-point-before
        (symbol-function ...)))
      :form
      (eq undercover--stop-point-before nil)
      :value nil))
   FAILED   1/11  test-001/edebug-handlers-are-setted (0.000376 sec)
   passed   2/11  test-002/result-is-correct (0.003881 sec)
   passed   3/11  test-003/functions-are-covered (0.000162 sec)
   passed   4/11  test-004/check-distance-stop-points-number-of-covers (0.000281 sec)
   passed   5/11  test-005/check-coverage-statistics (0.002042 sec)
   passed   6/11  test-006/check-environment-variables (0.000196 sec)
Test test-007/check-coveralls-report backtrace:
  (ad-deactivate 'undercover-safe-report)
  (progn (ad-deactivate 'undercover-safe-report) (undercover-safe-repo
  (unwind-protect (progn (ad-deactivate 'undercover-safe-report) (unde
  (let ((---old-env-var--- (getenv "TRAVIS"))) (setenv "TRAVIS" "true"
  (closure (t) nil (let ((---old-env-var--- (getenv "TRAVIS"))) (seten
  ert--run-test-internal(#s(ert--test-execution-info :test #s(ert-test
  ert-run-test(#s(ert-test :name test-007/check-coveralls-report :docu
  ert-run-or-rerun-test(#s(ert--stats :selector t :tests ... :test-map
  ert-run-tests(t #f(compiled-function (event-type &rest event-args) #
  ert-run-tests-batch(nil)
  ert-run-tests-batch-and-exit()
  eval((ert-run-tests-batch-and-exit) t)
  command-line-1(("-l" "package" "--eval" "(add-to-list 'package-direc
  command-line()
  normal-top-level()
Test test-007/check-coveralls-report condition:
    (void-function ad-deactivate)
   FAILED   7/11  test-007/check-coveralls-report (0.000232 sec)
   passed   8/11  test-008/should-error (0.001555 sec)
   passed   9/11  test-009/check-simplecov-report (0.004828 sec)
   passed  10/11  test-010/check-text-report (0.001997 sec)
   passed  11/11  test-011/check-text-report-file (0.002497 sec)

Ran 11 tests, 9 results as expected, 2 unexpected (2020-11-01 12:27:57+0500, 0.527562 sec)

2 unexpected results:
   FAILED  test-001/edebug-handlers-are-setted
   FAILED  test-007/check-coveralls-report

Error: (error "Unsupported report-format")
undercover-el / undercover.el

Tests fail with GNU Emacs 27.1 #62
