[Google App Engine Construindo serviços na nuvem] erro ao subir aplicação

O build da aplicação funciona normalmente porém ao tentar subir a aplicação como descrito no livro na pag 40, ocorre o seguinte erro:

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:: Spring Boot :: (v2.0.0.RELEASE)

2018-03-06 09:08:24.069 INFO 5321 — [ main] b.c.s.g.GaeExemplo1ApplicationTests : Starting GaeExemplo1ApplicationTests on unix-Inspiron-1564 with PID 5321 (started by unix in /home/unix/Downloads/gae_exemplo1)
2018-03-06 09:08:24.077 INFO 5321 — [ main] b.c.s.g.GaeExemplo1ApplicationTests : No active profile set, falling back to default profiles: default
2018-03-06 09:08:24.211 INFO 5321 — [ main] o.s.w.c.s.GenericWebApplicationContext : Refreshing org.springframework.web.context.support.GenericWebApplicationContext@4310d43: startup date [Tue Mar 06 09:08:24 BRT 2018]; root of context hierarchy
2018-03-06 09:08:27.120 INFO 5321 — [ main] s.w.s.m.m.a.RequestMappingHandlerAdapter : Looking for @ControllerAdvice: org.springframework.web.context.support.GenericWebApplicationContext@4310d43: startup date [Tue Mar 06 09:08:24 BRT 2018]; root of context hierarchy
2018-03-06 09:08:27.258 INFO 5321 — [ main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped “{[/error],produces=[text/html]}” onto public org.springframework.web.servlet.ModelAndView org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController.errorHtml(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)
2018-03-06 09:08:27.260 INFO 5321 — [ main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped “{[/error]}” onto public org.springframework.http.ResponseEntity<java.util.Map<java.lang.String, java.lang.Object>> org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController.error(javax.servlet.http.HttpServletRequest)
2018-03-06 09:08:27.352 INFO 5321 — [ main] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/webjars/] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2018-03-06 09:08:27.352 INFO 5321 — [ main] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/
] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2018-03-06 09:08:27.440 INFO 5321 — [ main] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/**/favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2018-03-06 09:08:27.807 INFO 5321 — [ main] b.c.s.g.GaeExemplo1ApplicationTests : Started GaeExemplo1ApplicationTests in 4.206 seconds (JVM running for 5.613)
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 5.38 s - in br.com.siecola.gae_exemplo1.GaeExemplo1ApplicationTests
2018-03-06 09:08:28.061 INFO 5321 — [ Thread-2] o.s.w.c.s.GenericWebApplicationContext : Closing org.springframework.web.context.support.GenericWebApplicationContext@4310d43: startup date [Tue Mar 06 09:08:24 BRT 2018]; root of context hierarchy
[INFO]
[INFO] Results:
[INFO]
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0
[INFO]
[INFO]
[INFO] — maven-war-plugin:3.1.0:war (default-war) @ gae_exemplo1 —
[INFO] Packaging webapp
[INFO] Assembling webapp [gae_exemplo1] in [/home/unix/Downloads/gae_exemplo1/target/gae_exemplo1-0.0.1-SNAPSHOT]
[INFO] Processing war project
[INFO] Copying webapp resources [/home/unix/Downloads/gae_exemplo1/src/main/webapp]
[INFO] Webapp assembled in [139 msecs]
[INFO] Building war: /home/unix/Downloads/gae_exemplo1/target/gae_exemplo1-0.0.1-SNAPSHOT.war
[INFO]
[INFO] — spring-boot-maven-plugin:2.0.0.RELEASE:repackage (default) @ gae_exemplo1 —
[INFO]
[INFO] <<< appengine-maven-plugin:1.3.1:run (default-cli) < package @ gae_exemplo1 <<<
[INFO]
[INFO] — appengine-maven-plugin:1.3.1:run (default-cli) @ gae_exemplo1 —
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 13.712 s
[INFO] Finished at: 2018-03-06T09:08:32-03:00
[INFO] Final Memory: 29M/255M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal com.google.cloud.tools:appengine-maven-plugin:1.3.1:run (default-cli) on project gae_exemplo1: Execution default-cli of goal com.google.cloud.tools:appengine-maven-plugin:1.3.1:run failed: The Google Cloud SDK could not be found in the customary locations and no path was provided. -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/PluginExecutionException

Process finished with exit code 1