Check if zmq is installed in tests, update docs

Github-Pull: #7635
Rebased-From: 2ab835a

README.md

@@ -55,10 +55,10 @@ submit new unit tests for old code. Unit tests can be compiled and run
 
 There are also [regression and integration tests](/qa) of the RPC interface, written
 in Python, that are run automatically on the build server.
-These tests can be run with: `qa/pull-tester/rpc-tests.py`
+These tests can be run (if the [test dependencies](/qa) are installed) with: `qa/pull-tester/rpc-tests.py`
 
 The Travis CI system makes sure that every pull request is built for Windows
-and Linux, OSX, and that unit and sanity tests are automatically run.
+and Linux, OS X, and that unit and sanity tests are automatically run.
 
 ### Manual Quality Assurance (QA) Testing
 

qa/README.md

@@ -5,6 +5,17 @@ Every pull request to the bitcoin repository is built and run through
 the regression test suite. You can also run all or only individual
 tests locally.
 
+Test dependencies
+=================
+Before running the tests, the following must be installed.
+
+Unix
+----
+The python-zmq library is required. On Ubuntu or Debian it can be installed via: 
+```
+sudo apt-get install python-zmq
+```
+
 Running tests
 =============
 

qa/pull-tester/rpc-tests.py

@@ -40,6 +40,15 @@
     ENABLE_UTILS=0
 if 'ENABLE_ZMQ' not in vars():
     ENABLE_ZMQ=0
+    
+# python-zmq may not be installed. Handle this gracefully and with some helpful info
+if ENABLE_ZMQ:
+    try:
+        import zmq
+    except ImportError:
+        print("WARNING: \"import zmq\" failed. Setting ENABLE_ZMQ=0. " \
+            "To run zmq tests, see dependency info in /qa/README.md.")
+        ENABLE_ZMQ=0
 
 ENABLE_COVERAGE=0