String rawChildModelVersion = childModel.getVersion();

                if (rawChildModelVersion == null) {
                    // Message below is checked for in the MNG-2199 core IT.
                    problems.add(
                            Severity.FATAL,
                            ModelProblem.Version.V31,
                            "Version must be a constant",

                            if (logger.isDebugEnabled()) {
                                // Message below is checked for in the MNG-2199 core IT.
                                logger.warn("Failed to build parent project for " + project.getId(), e);
                            } else {
                                // Message below is checked for in the MNG-2199 core IT.

                    && versionRangeResult.getVersionConstraint().getRange() != null
                    && versionRangeResult.getVersionConstraint().getRange().getUpperBound() == null) {
                // Message below is checked for in the MNG-2199 core IT.
                throw new UnresolvableModelException(
                        String.format(
                                "The requested parent version range '%s' does not specify an upper bound",

            if (coord.getVersion().getVersionRange() != null
                    && coord.getVersion().getVersionRange().getUpperBoundary() == null) {
                // Message below is checked for in the MNG-2199 core IT.
                throw new ModelResolverException(
                        String.format("The requested version range '%s' does not specify an upper bound", version),
                        groupId,

            Maven required to use the resulting plugin.<br>
            In Maven 2, this was also specifying the minimum version of Maven required to build a
            project, but this usage is <b>deprecated</b> in Maven 3 and not checked any more: use
            the <a href="https://maven.apache.org/enforcer/enforcer-rules/requireMavenVersion.html">Maven Enforcer Plugin's
            {@code requireMavenVersion} rule</a> instead.
            ]]>

                    }
                }

                // TODO should this be inside the above check?
                // touch file so that this is not checked again until interval has passed
                if (file.exists()) {
                    file.setLastModified(System.currentTimeMillis());
                }
            }
        }

        try {