Add option to ignore import errors in doctests

--HG--
branch : ignore-doctest-import-errors

_pytest/doctest.py

@@ -17,6 +17,10 @@ def pytest_addoption(parser):
         action="store", default="test*.txt", metavar="pat",
         help="doctests file matching pattern, default: test*.txt",
         dest="doctestglob")
+    group.addoption("--doctest-ignore-import-errors",
+        action="store_true", default=False,
+        help="ignore doctest ImportErrors",
+        dest="doctest_ignore_import_errors")
 
 def pytest_collect_file(path, parent):
     config = parent.config
@@ -130,7 +134,13 @@ class DoctestModule(pytest.File):
         if self.fspath.basename == "conftest.py":
             module = self.config._conftest.importconftest(self.fspath)
         else:
+            try:
                 module = self.fspath.pyimport()
+            except ImportError:
+                if self.config.getvalue('doctest_ignore_import_errors'):
+                    pytest.skip('unable to import module %r' % self.fspath)
+                else:
+                    raise
         # satisfy `FixtureRequest` constructor...
         self.funcargs = {}
         self._fixtureinfo = FuncFixtureInfo((), [], {})