When creating a virtualenv for Galaxy, prefer python 2.7.

Author: jmchilton

planemo/commands/cmd_virtualenv.py

@@ -11,14 +11,16 @@
 
 
 @click.command("virtualenv")
+@click.option("-p", "--python",
+              metavar="PYTHON_EXE")
 @click.argument("virtualenv_path",
                 metavar="VIRTUALENV_PATH",
                 type=VIRTUALENV_PATH_TYPE)
 @pass_context
-def cli(ctx, virtualenv_path):
+def cli(ctx, virtualenv_path, **kwds):
     """Create a virtualenv.
 
     Use virtualenv as library to create a virtualenv for Galaxy if virtualenv
     is not available on the PATH.
     """
-    virtualenv.create_and_exit(virtualenv_path)
+    virtualenv.create_and_exit(virtualenv_path, **kwds)

planemo/virtualenv.py

@@ -9,8 +9,11 @@
 from galaxy.tools.deps.commands import which
 
 
-def create_and_exit(virtualenv_path):
+def create_and_exit(virtualenv_path, **kwds):
     sys.argv = ["virtualenv", virtualenv_path]
+    python = kwds.get("python", None)
+    if python:
+        sys.argv.extend(["--python", python])
     return virtualenv.main()
 
 
@@ -21,6 +24,21 @@ def create_command(virtualenv_path):
     planemo_path = os.path.abspath(sys.argv[0])
     virtualenv_on_path = which("virtualenv")
     if virtualenv_on_path:
-        return " ".join([os.path.abspath(virtualenv_on_path), virtualenv_path])
+        base_command = [
+            os.path.abspath(virtualenv_on_path),
+        ]
     else:
-        return " ".join([planemo_path, "virtualenv", virtualenv_path])
+        base_command = [
+            planemo_path, "virtualenv",
+        ]
+
+    command = base_command
+
+    # If planemo is running in a Python 3 environment but Python 2.7
+    # is available for Galaxy, use it.
+    python27 = which("python2.7")
+    if python27:
+        python27 = os.path.abspath(python27)
+        command.extend(["-p", python27])
+    command.append(virtualenv_path)
+    return " ".join(command)