routes: PyPi 2.3.1 and 2.4 packages missing

$ pip install -I Routes==2.3.1
Could not find a version that satisfies the requirement Routes==2.3.1 (from versions: 1.5, 1.5.1, 1.5.2, 1.6, 1.6.1, 1.6.2, 1.6.3, 1.7, 1.7.1, 1.7.2, 1.7.3, 1.8, 1.9, 1.9.1, 1.9.2, 1.10, 1.10.1, 1.10.2, 1.10.3, 1.11, 1.12, 1.12.1, 1.12.3, 1.13, 2.0, 2.1, 2.2, 2.3)                                                                                                                                                                                                                
No matching distribution found for Routes==2.3.1

$ pip install -I Routes==2.4
Could not find a version that satisfies the requirement Routes==2.4 (from versions: 1.5, 1.5.1, 1.5.2, 1.6, 1.6.1, 1.6.2, 1.6.3, 1.7, 1.7.1, 1.7.2, 1.7.3, 1.8, 1.9, 1.9.1, 1.9.2, 1.10, 1.10.1, 1.10.2, 1.10.3, 1.11, 1.12, 1.12.1, 1.12.3, 1.13, 2.0, 2.1, 2.2, 2.3)                                                                                                                                                                                                                  
No matching distribution found for Routes==2.4