blacklist backports.lzma v0.0.4

backports.lzma recently bumped up to v0.0.4, adding namespace support
to the package. However, they forgot to call declare_namespace() in
their __init__.py. This causes pip install failures when running

    pip install file:///docker-registry#egg=docker-registry

From inside the Dockerfile.

Author: Matthew Fisher

setup.py

@@ -21,7 +21,7 @@
 
 if ver < (3, 0):
     # Python 2 requires lzma backport
-    requirements.insert(0, 'backports.lzma>=0.0.2')
+    requirements.insert(0, 'backports.lzma>=0.0.2,!=0.0.4')
     if ver < (2, 7):
         # Python 2.6 requires additional libraries
         requirements.insert(0, 'argparse>=1.2.1')