Uppdated! "Cannot determine the default location of the Google Cloud SDK" Solved

Error

Got a really annoying error while trying to run my local Flexible Environment with GCloud 
$ mvn -Dgcloud.gcloud_directory="c:\path\to\gcloud-sdk\" gcloud:run
[ERROR] Cannot determine the default location of the Google Cloud SDK.
[ERROR] If you need to install the Google Cloud SDK, follow the instructions located at https://cloud.google.com/appengine/docs/java/managed-vms
[ERROR] You can then set it via <gcloud_directory> </gcloud_directory> in the pom.xml
[ERROR]
org.apache.maven.plugin.MojoExecutionException: Unkown Google Cloud SDK location:C:\...\gcloud_sdk
        at com.google.appengine.gcloudapp.AbstractGcloudMojo.setupInitialCommands(AbstractGcloudMojo.java:170)
        at com.google.appengine.gcloudapp.GCloudAppRun.getCommand(GCloudAppRun.java:306)
        at com.google.appengine.gcloudapp.GCloudAppRun.execute(GCloudAppRun.java:292)
        at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:207)
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
        at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:116)
        at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:80)
        at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51)
        at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
        at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:307)
        at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:193)
        at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:106)
        at org.apache.maven.cli.MavenCli.execute(MavenCli.java:863)
        at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:288)
        at org.apache.maven.cli.MavenCli.main(MavenCli.java:199)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
        at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
        at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
        at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 3.441 s
[INFO] Finished at: 2016-05-30T20:21:34+02:00
[INFO] Final Memory: 24M/380M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal com.google.appengine:gcloud-maven-plugin:2.0.9.74.v20150814:run (default-cli) on project scala-js-compiler: Execution error: org.apache.maven.plugin.MojoExecutionException: Unkown Google Cloud SDK location:C:...\gcloud_sdk -> [Help 1]

Solution

It was much easier to solve! Just add Python to path (which is bundled in the Gcloud SDK).

But managed to use the locally installed python to run the python script which starts development server:
$ cd project
$ c:\...\gcloud_sdk\google-cloud-sdk\platform\bundledpython\python.exe c:\...\gcloud_sdk\google-cloud-sdk\bin\dev_appserver.py src\main\webapp