Try to fix Windows path issue with new custom step

On windows, using '/' in pathnames won't work, so it's impossible to use
to describe a path in a feature spec. The solution is to move the path
logic out of the feature spec and hand it over to `os.path.join` in a
new custom step for userscripts.

tests/integration/features/conftest.py

@@ -129,11 +129,23 @@ def run_command(quteproc, httpbin, command):
     else:
         count = None
     command = command.replace('(port)', str(httpbin.port))
-    command = command.replace('(datapath)', utils.abs_datapath(__file__))
 
     quteproc.send_cmd(command, count=count)
 
 
+@bdd.when(bdd.parsers.parse("I execute the userscript {userscript}"))
+def run_userscript(quteproc, userscript):
+    """Run a userscript located in tests/integration/data/userscripts.
+
+    Wrapper around :spawn --userscript {userscript} that uses an absolute
+    path.
+    """
+    abs_userscript_path = os.path.join(utils.abs_datapath(__file__),
+                                       'userscripts', userscript)
+    cmd = ':spawn --userscript {abs_userscript_path}'
+    quteproc.send_cmd(cmd.format(abs_userscript_path=abs_userscript_path))
+
+
 @bdd.when(bdd.parsers.parse("I reload"))
 def reload(qtbot, httpbin, quteproc, command):
     """Reload and wait until a new request is received."""

tests/integration/features/spawn.feature

@@ -17,7 +17,7 @@ Feature: :spawn
         Then "Executing echo with args ['about:blank'], userscript=False" should be logged
 
     Scenario: Running :spawn with userscript
-        When I run :spawn --userscript (datapath)/userscripts/open_current_url
+        When I execute the userscript open_current_url
         And I wait until about:blank is loaded
         Then the following tabs should be open:
             - about:blank