Add comment back in

tox.ini

@@ -94,6 +94,7 @@ commands =
     # Add this so that coverage will run on subprocesses
     /bin/sh -c 'echo "import coverage; coverage.process_startup()" > {envsitepackagesdir}/../sitecustomize.py'
 
+    # Install Synapse itself. This won't update any libraries.
     pip install -e .
 
     {envbindir}/coverage run "{envbindir}/trial"  {env:TRIAL_FLAGS:} {posargs:tests} {env:TOXSUFFIX:}