Merge pull request #2888 from bachp/pynacl-1.2.1

Update pynacl dependency to 1.2.1 or higher

synapse/python_dependencies.py

@@ -24,7 +24,7 @@
     "unpaddedbase64>=1.1.0": ["unpaddedbase64>=1.1.0"],
     "canonicaljson>=1.0.0": ["canonicaljson>=1.0.0"],
     "signedjson>=1.0.0": ["signedjson>=1.0.0"],
-    "pynacl==0.3.0": ["nacl==0.3.0", "nacl.bindings"],
+    "pynacl>=1.2.1": ["nacl>=1.2.1", "nacl.bindings"],
     "service_identity>=1.0.0": ["service_identity>=1.0.0"],
     "Twisted>=16.0.0": ["twisted>=16.0.0"],
     "pyopenssl>=0.14": ["OpenSSL>=0.14"],