Revert the tmt lint schema failure (teemtee#4481)

The original intention was to implement what is said in this
[comment](teemtee#4445 (comment)).
The issue I ran into is that when I have `tmt lint` emit a schema (pass
or warn) if the only error is the `detect_missing_required_properties`,
then it still fails because almost always this check
`detect_enum_violations` also fails when a required key is missing.
`detect_enum_violations` is triggered when `how` is used and the
required key is missing because it cycles through all of the values and
tells you when the first 9/10 did not match.

Cursor analysis of why this occurs (better explanation than mine):
> Explaining why enum violations only appear when the required property
is missing:
> The schema uses `oneOf` for the report step, which requires exactly
one schema to match. Here's what happens:
> When the `project` key (required property) is present:
> The `reportportal` schema matches (`how: reportportal` and `project`
are present)
> Since `oneOf` requires exactly one match and reportportal matches,
validation succeeds
> No enum violations occur because the validator doesn't try other
schemas
> When the `project` key (required property) is missing:
> The `reportportal` schema fails (missing required `project`)
> Since `oneOf` requires exactly one match and `reportportal` failed,
the validator tries other schemas (display, html, junit, polarion)
> Each alternative fails because `how: reportportal` doesn't match their
enum values (they expect how: display, how: html, etc.)
> These enum violations are reported as the validator tries each
alternative

So, it's not simple to turn _only_ the missing required key into a
warning in `tmt lint` since even if that error is not counted, another
error still occurs, still resulting in an overall `tmt lint` failure.

After some discussion with @LecrisUT, @happz, and @thrix, reverting the
FAIL to a WARN would unblock the CI failures for teemtee#4178, while we work on
a better overall solution where teemtee#3618 can be reimplemented, and teemtee#4178 is
still resolved. The ticket for the better solution is teemtee#4483

This PR reverts the tmt lint schema failure implemented to fix issue
teemtee#3618.

Fixes: teemtee#4178

Author: tcornell-bus

docs/releases/pending/4178.fmf

@@ -0,0 +1,6 @@
+description: |
+    The ``tmt lint`` command no longer fails with an
+    exit code 1 when any schema validation warnings are emitted,
+    it now emits a warn with an exit code 0. This reverts the
+    behavior added in tmt-1.55.0, until a better solution can
+    be implemented.

tests/lint/all/test.sh

@@ -62,7 +62,7 @@ rlJournalStart
     rlPhaseEnd
 
     rlPhaseStartTest "Check --fix for tests"
-        rlRun -s "tmt lint --fix fix" 1 "Fix the test"
+        rlRun -s "tmt lint --fix fix" 0 "Fix the test"
         rlAssertGrep 'relevancy converted into adjust' $rlRun_LOG
         rlRun -s "tmt lint fix" 0 "Should pass after fix"
     rlPhaseEnd

tests/lint/plan/test.sh

@@ -43,7 +43,7 @@ rlJournalStart
         rlAssertGrep "warn C000 value of \"how\" is not \"fmf\"" $rlRun_LOG
         rlAssertGrep "warn C000 value of \"how\" is not \"tmt\"" $rlRun_LOG
         rlAssertGrep "warn C000 value of \"how\" is not \"upgrade\"" $rlRun_LOG
-        rlAssertGrep "fail C000 fmf node failed schema validation" $rlRun_LOG
+        rlAssertGrep "warn C000 fmf node failed schema validation" $rlRun_LOG
         rlAssertGrep "fail P003 unknown execute method \"somehow\" in \"default-0\"" $rlRun_LOG
         rlAssertGrep "fail P004 unknown discover method \"somehow\" in \"default-0\"" $rlRun_LOG
 
@@ -62,13 +62,13 @@ rlJournalStart
         rlAssertGrep "fail P005 remote fmf id in \"b\" is invalid, repo 'http://invalid-url' cannot be cloned" $rlRun_LOG
 
         rlRun -s "$tmt plan lint invalid_attr" 1
-        rlAssertGrep "fail C000 fmf node failed schema validation" $rlRun_LOG
+        rlAssertGrep "warn C000 fmf node failed schema validation" $rlRun_LOG
         rlAssertGrep "warn C001 summary key is missing" $rlRun_LOG
         rlAssertGrep "fail P001 unknown key \"discove\" is used" $rlRun_LOG
         rlAssertGrep "fail P001 unknown key \"environmen\" is used" $rlRun_LOG
         rlAssertGrep "fail P001 unknown key \"summaryABCDEF\" is used" $rlRun_LOG
 
-        rlRun -s "$tmt plan lint invalid-plugin-key" 1
+        rlRun -s "$tmt plan lint invalid-plugin-key" 0
         rlAssertGrep 'warn C000 key "wrong" not recognized by schema$' $rlRun_LOG
         rlAssertGrep 'warn C000 key "wrong" not recognized by schema /schemas/prepare/feature' $rlRun_LOG
 
@@ -96,8 +96,9 @@ rlJournalStart
     rlPhaseEnd
 
     rlPhaseStartTest "Lint of missing required property"
-        rlRun -s "$tmt plan lint missing_required" 1
+        rlRun -s "$tmt plan lint missing_required" 0
         rlAssertGrep "warn C000 \"project-id\" is a required property by schema /schemas/report/polarion" "$rlRun_LOG"
+        rlAssertGrep "warn C000 fmf node failed schema validation" "$rlRun_LOG"
     rlPhaseEnd
 
     rlPhaseStartTest "Lint of duplicate ids"

tests/lint/story/test.sh

@@ -20,12 +20,12 @@ rlJournalStart
         rlAssertGrep "warn C001 summary should not exceed 50 characters" $rlRun_LOG
 
         rlRun -s "tmt stories lint typo_in_key" 1
-        rlAssertGrep "fail C000 fmf node failed schema validation" $rlRun_LOG
+        rlAssertGrep "warn C000 fmf node failed schema validation" $rlRun_LOG
         rlAssertGrep "warn C001 summary key is missing" $rlRun_LOG
         rlAssertGrep "fail S001 unknown key \"exampleGG\" is used" $rlRun_LOG
 
         rlRun -s "tmt stories lint missing_story" 1
-        rlAssertGrep "fail C000 fmf node failed schema validation" $rlRun_LOG
+        rlAssertGrep "warn C000 fmf node failed schema validation" $rlRun_LOG
         rlAssertGrep "warn C001 summary key is missing" $rlRun_LOG
         rlAssertGrep "pass S001 correct keys are used" $rlRun_LOG
         rlAssertGrep "fail S002 story is required" $rlRun_LOG

tests/lint/test/test.sh

@@ -28,9 +28,9 @@ rlJournalStart
     rlPhaseEnd
 
     rlPhaseStartTest "Old yaml"
-        rlRun -s "tmt test lint old-yaml" 1
+        rlRun -s "tmt test lint old-yaml" 0
         rlAssertGrep "warn: /old-yaml:enabled - 'yes' is not of type 'boolean'" $rlRun_LOG
-        rlAssertGrep 'fail C000 fmf node failed schema validation' $rlRun_LOG
+        rlAssertGrep 'warn C000 fmf node failed schema validation' $rlRun_LOG
     rlPhaseEnd
 
     rlPhaseStartTest "Bad"
@@ -53,15 +53,15 @@ rlJournalStart
         rlAssertGrep "fail T001 unknown key \"serial_number\" is used" $rlRun_LOG
         rlRun -s "tmt test lint coverage" 1
         rlAssertGrep "fail T006 the 'coverage' field has been obsoleted by 'link'" $rlRun_LOG
-        rlRun -s "tmt test lint library-missing-url-path" 1
-        rlAssertGrep 'fail C000 fmf node failed schema validation' $rlRun_LOG
+        rlRun -s "tmt test lint library-missing-url-path" 0
+        rlAssertGrep 'warn C000 fmf node failed schema validation' $rlRun_LOG
         rlAssertGrep 'is not valid under any of the given schemas' $rlRun_LOG
     rlPhaseEnd
 
     rlPhaseStartTest "Fix"
         # With --fix relevancy should be converted
-        rlRun -s "tmt test lint --fix relevancy" 1
-        rlAssertGrep 'fail C000 fmf node failed schema validation' $rlRun_LOG
+        rlRun -s "tmt test lint --fix relevancy" 0
+        rlAssertGrep 'warn C000 fmf node failed schema validation' $rlRun_LOG
         rlAssertGrep 'fix  T005 relevancy converted into adjust' $rlRun_LOG
         # Re-run after --fix fixed the plan
         rlRun -s "tmt test lint --fix relevancy" 0

tmt/base.py

@@ -1185,7 +1185,7 @@ def detect_errors(error: jsonschema.ValidationError) -> LinterReturn:
                     for suberror in error.context:
                         yield from detect_errors(suberror)
 
-            yield LinterOutcome.FAIL, 'fmf node failed schema validation'
+            yield LinterOutcome.WARN, 'fmf node failed schema validation'
 
             return