With Tycho 2.7.1 the APP4MC Platform build breaks on building the 3rd party feature. It shows the following error message:

Execution default-package-feature of goal org.eclipse.tycho:tycho-packaging-plugin:2.7.1:package-feature failed: Neither raw version nor format was specified: null

With a verbose output I can see the following exception:

Caused by: java.lang.IllegalArgumentException: Neither raw version nor format was specified: null
at org.eclipse.equinox.internal.p2.metadata.VersionParser.parse (VersionParser.java:155)
at org.eclipse.equinox.p2.metadata.Version.create (Version.java:96)
at org.eclipse.equinox.p2.metadata.Version.parseVersion (Version.java:164)
at org.eclipse.equinox.p2.publisher.eclipse.FeatureEntry. (FeatureEntry.java:66)
at org.eclipse.equinox.p2.publisher.eclipse.FeatureEntry.createRequires (FeatureEntry.java:43)
at org.eclipse.tycho.p2.target.ArtifactMatcher.getVersionRangeFromImport (ArtifactMatcher.java:89)
at org.eclipse.tycho.p2.target.TargetPlatformBaseImpl.resolveArtifact (TargetPlatformBaseImpl.java:100)
at org.eclipse.tycho.packaging.FeatureXmlTransformer.resolvePluginReference (FeatureXmlTransformer.java:111)
at org.eclipse.tycho.packaging.FeatureXmlTransformer.expandReferences (FeatureXmlTransformer.java:83)
at org.eclipse.tycho.packaging.PackageFeatureMojo.expandVersionQualifiers (PackageFeatureMojo.java:258)
at org.eclipse.tycho.packaging.PackageFeatureMojo.execute (PackageFeatureMojo.java:124)

The feature.xml of the project that fails is located here:
https://git.eclipse.org/c/app4mc/org.eclipse.app4mc.git/tree/features/org.eclipse.app4mc.platform.3rdparty/feature.xml?h=develop