Minimal correction for #148: Reducing LogOutput

src/main/java/at/ac/uibk/gitsearch/web/rest/ExerciseResource.java

@@ -51,7 +51,7 @@ public class ExerciseResource {
         try {
             repositoryStream = gitLabService.getRepositoryFile(exerciseId, filePath);
         } catch (IOException | GitLabApiException e) {
-            log.error("Cannot read file for exercise {} and path {}", exerciseId, filePath, e);
+            log.warn("Cannot read file for exercise {} and path {}: {}", exerciseId, filePath, e.getMessage());
             return ResponseEntity.notFound().headers(HeaderUtil.createFailureAlert(applicationName, true, "RepositoryFile", "not found",
                     "There was an error on the server and the resource file could not be created.")).build();        }