Check if zmq is installed in tests, update docs

Github-Pull: #7635
Rebased-From: 2ab835ae6c02de14264896d571c0bba230a1e9f0

README.md

@@ -55,7 +55,7 @@ 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, OS X, and that unit and sanity tests are automatically run.

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

@@ -41,6 +41,15 @@ if 'ENABLE_UTILS' not in vars():
 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
 
 #Create a set to store arguments and create the passOn string