enable test coverage on coveralls

.travis.yml

@@ -19,11 +19,17 b' before_install:'
     - git clone --quiet --depth 1 https://github.com/minrk/travis-wheels travis-wheels
     - 'if [[ $GROUP == js* ]]; then python -m IPython.external.mathjax; fi'
 install:
+    - pip install coveralls
     - pip install -f travis-wheels/wheelhouse file://$PWD#egg=ipython[all]
 script:
-    - cd /tmp && iptest $GROUP
+    - cd /tmp && iptest $GROUP --coverage xml && cd -
 
 matrix:
     exclude:
         - python: 3.3
           env: GROUP=js
+
+after_success:
+    - cp /tmp/ipy_coverage.xml ./
+    - cp /tmp/.coverage ./
+    - coveralls

IPython/testing/iptestcontroller.py

@@ -636,7 +636,7 b' def run_iptestall(options):'
         print()
 
     if options.coverage:
-        from coverage import coverage
+        from coverage import coverage, CoverageException
         cov = coverage(data_file='.coverage')
         cov.combine()
         cov.save()
@@ -671,7 +671,10 b' def run_iptestall(options):'
 
         # Coverage XML report
         elif options.coverage == 'xml':
-            cov.xml_report(outfile='ipy_coverage.xml')
+            try:
+                cov.xml_report(outfile='ipy_coverage.xml')
+            except CoverageException:
+                pass
 
     if failed:
         # Ensure that our exit code indicates failure