as msgpack-python 0.4.6 is released now, just use that.

setup.py

@@ -122,14 +122,7 @@ setup(
     scripts=['scripts/attic'],
     cmdclass=cmdclass,
     ext_modules=ext_modules,
-    # msgpack pure python data corruption in some versions.
-    # The compiled C-version of python-msgpack was not affected.
-    # So, IF you had a compiler installed AND you did not force the pure-python version,
-    # you likely were not affected by the issue.
-    # python-msgpack <=0.4.2 is OK, 0.4.5 is latest release, but bug was fixed in repo.
-    # Details see:
-    # https://github.com/jborg/attic/issues/171
-    # https://github.com/jborg/attic/issues/185
-    # https://github.com/msgpack/msgpack-python/issues/124
-    install_requires=['msgpack-python<=0.4.2,>0.4.5']
+    # msgpack pure python data corruption was fixed in 0.4.6.
+    # Also, we might use some rather recent API features.
+    install_requires=['msgpack-python>=0.4.6']
 )