travis: Ignore doc changes when building a PR

Fixes #1441

scripts/dev/check_doc_changes.py

@@ -22,8 +22,15 @@
 
 import sys
 import subprocess
+import os
 
 code = subprocess.call(['git', '--no-pager', 'diff', '--exit-code', '--stat'])
+
+if os.environ.get('TRAVIS_PULL_REQUEST', 'false') != 'false':
+    if code != 0:
+        print("Docs changed but ignoring change as we're building a PR")
+    sys.exit(0)
+
 if code != 0:
     print()
     print('The autogenerated docs changed, please run this to update them:')

tox.ini

@@ -190,13 +190,13 @@ commands =
 basepython = python3
 skip_install = true
 whitelist_externals = git
-passenv =
+passenv = TRAVIS_PULL_REQUEST
 deps =
     -r{toxinidir}/requirements.txt
 commands =
     {envpython} scripts/link_pyqt.py --tox {envdir}
     {envpython} scripts/dev/src2asciidoc.py {posargs}
-    {envpython} scripts/dev/check_doc_changes.py
+    {envpython} scripts/dev/check_doc_changes.py {posargs}
     {envpython} scripts/asciidoc2html.py {posargs}
 
 [testenv:cxfreeze-windows]