How to use gradle-enterprise-maven-extension behind a proxy? - maven

Question

Willing to use the gradle-enterprise-maven-extension
to migrate a project from maven to gradle,
I cloned the maven-build-scan-quickstart provided by the gradle team.
But runing mvn install, as specified, after acceptation of gradle terms of service,
I receive the following message:
UnknownHostException: scans-in.gradle.com
I tried to configure the proxy in several manners:
Using commannd line option:
mvn install -Dhttps.proxyHost=localhost:8888 -Dhttps.proxyPort=localhost:8888
Using a gradle.properties file in a directory at %GRADLE_USER_HOME% directory location:
(proxy is also configured in maven's settings.xml and need no password it works fine when using maven in standard ways)
gradle.properties :
systemProp.http.proxyHost=localhost
systemProp.http.proxyPort=8888
systemProp.http.nonProxyHosts=*.nonproxyrepos.com|localhost|127.0.0.1
systemProp.https.proxyHost=localhost
systemProp.https.proxyPort=8888
systemProp.https.nonProxyHosts=*.nonproxyrepos.com|localhost|127.0.0.1
But I still receive the same message:
~/github/maven-build-scan-quickstart
$ mvn install
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 3.830 s
[INFO] Finished at: 2019-12-31T13:09:19+01:00
[INFO] ------------------------------------------------------------------------
[INFO] 7 goals, 7 executed
Publishing a build scan to scans.gradle.com requires accepting the Gradle Terms of Service defined at https://gradle.com/terms-of-service. Do you accept these terms? (yes/no): yes
[INFO] Gradle Terms of Service accepted.
[INFO]
[INFO] Publishing build scan...
[INFO]
[INFO] A network error occurred.
[INFO]
[INFO] The hostname 'scans-in.gradle.com' could not be resolved.
[INFO] You may be disconnected from the Internet.
[INFO]
[INFO] If you require assistance with this problem, please report it via https://gradle.com/help/plugin and include the following information via copy/paste.
[INFO]
[INFO] ----------
[INFO] Maven version: 3.6.2
[INFO] Extension version: 1.3.3
[INFO] Request URL: https://scans-in.gradle.com/in/maven/3.6.2/1.3.3
[INFO] Request ID: 1234567e-abcd-23de-c2d3-3fbbccd14a32
[INFO] Exception: java.net.UnknownHostException: scans-in.gradle.com
[INFO] ----------
[INFO]