Reduce classpath scanner logging (#3099)

When `cucumber.glue` is not configured Cucumber scans the entire
classpath for glue. This "just works". However, when scanning encounters
a class with missing dependencies Cucumber log complain quite loudly
about this.

The assumption was that this scenario would be quite rare, and it was
until IDEA (intentionally and on request) stopped setting
`cucumber.glue`. Now it is no longer a rare occurance.

Author: mpkorstanje

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 ### Fixed
 - [Core] Prefer URIs with authority ([#3098](https://github.com/cucumber/cucumber-jvm/pull/3098) M.P. Korstanje)
+- [Core] Reduce classpath scanner logging ([#3099](https://github.com/cucumber/cucumber-jvm/pull/3099) M.P. Korstanje)
 
 ### Added
 - [Core] Add a `UsageJsonFormatter`, use with `--plugin usage-json` ([#3086](https://github.com/cucumber/cucumber-jvm/pull/3086) M.P. Korstanje)

cucumber-core/src/main/java/io/cucumber/core/resource/ClasspathScanner.java

@@ -14,7 +14,6 @@
 import java.util.function.Predicate;
 import java.util.function.Supplier;
 
-import static io.cucumber.core.resource.ClasspathSupport.classPathScanningExplanation;
 import static io.cucumber.core.resource.ClasspathSupport.determineFullyQualifiedClassName;
 import static io.cucumber.core.resource.ClasspathSupport.getUrisForPackage;
 import static io.cucumber.core.resource.ClasspathSupport.requireValidPackageName;
@@ -106,7 +105,8 @@ private Optional<Class<?>> safelyLoadClass(String fqn) {
         try {
             return Optional.ofNullable(getClassLoader().loadClass(fqn));
         } catch (ClassNotFoundException | NoClassDefFoundError e) {
-            log.warn(e, () -> "Failed to load class '" + fqn + "'.\n" + classPathScanningExplanation());
+            log.debug(e, () -> "Could not to load class '" + fqn
+                    + "'. If this is not a Glue class you can ignore this exception.\n");
         }
         return Optional.empty();
     }