GNU grep from 3.8 emitting warnings when invoking egrep/fgrep
https://build.opensuse.org/request/show/1001674

> egrep and fgrep commands, deprecated since 2007, now warn that
> they are obsolescent and should be replaced by grep -E / -F

From
https://build.opensuse.org/package/live_build_log/openSUSE:Factory:Staging:N/qpdf/standard/x86_64

[  266s] Running ../qtest/qpdf.test
[  266s] qpdf test 603 (check non-static ID version) FAILED
[  266s] cwd: /home/abuild/rpmbuild/BUILD/qpdf-10.6.3/qpdf/qtest/qpdf
[  266s] command: sh ./diff-ignore-ID-version a.pdf b.pdf
[  266s]  at qpdf.test line 1725.
[  266s] --> BEGIN EXPECTED OUTPUT <--
[  266s] okay
[  266s] --> END EXPECTED OUTPUT <--
[  266s] --> BEGIN ACTUAL OUTPUT <--
[  266s] egrep: warning: egrep is obsolescent; using grep -E
[  266s] egrep: warning: egrep is obsolescent; using grep -E
[  266s] egrep: warning: egrep is obsolescent; using grep -E
[  266s] okay
[  266s] --> END ACTUAL OUTPUT <--
[  266s] --> DIFF EXPECTED ACTUAL <--
[  266s] --- /tmp/testtemp.13811/expected    2022-09-08 02:09:09.120000000
+0000
[  266s] +++ /tmp/testtemp.13811/actual    2022-09-08 02:09:09.120000000 +0000
[  266s] @@ -1 +1,4 @@
[  266s] +egrep: warning: egrep is obsolescent; using grep -E
[  266s] +egrep: warning: egrep is obsolescent; using grep -E
[  266s] +egrep: warning: egrep is obsolescent; using grep -E
[  266s]  okay
[  266s] --> END DIFFERENCES <--
[  266s] qpdf test 1851 (check against base) FAILED