Problem with proxy authentication

[vglvnv]

Plugin version: latest. TeamCity version - 9.1.6 (build 37459).
When using proxy authentication, every test sending a notification fails:

[2016-03-29 16:19:10,070]  ERROR -   jetbrains.buildServer.SERVER - Error java.lang.NoSuchMethodError: org.apache.commons.codec.binary.Base64.<init>(I)V while processing request:...
java.lang.NoSuchMethodError: org.apache.commons.codec.binary.Base64.<init>(I)V
    at org.apache.http.impl.auth.BasicScheme.<init>(BasicScheme.java:65)
    at org.apache.http.impl.auth.BasicSchemeFactory.create(BasicSchemeFactory.java:68)
    at org.apache.http.impl.client.AuthenticationStrategyImpl.select(AuthenticationStrategyImpl.java:175)
    at org.apache.http.impl.client.ProxyAuthenticationStrategy.select(ProxyAuthenticationStrategy.java:43)
    at org.apache.http.impl.auth.HttpAuthenticator.handleAuthChallenge(HttpAuthenticator.java:154)
    at org.apache.http.impl.execchain.MainClientExec.createTunnelToTarget(MainClientExec.java:466)
    at org.apache.http.impl.execchain.MainClientExec.establishRoute(MainClientExec.java:380)
    at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:219)
    at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:195)
    at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:86)
    at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:108)
    at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:184)
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:82)
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:106)
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:57)
    at slacknotifications.SlackNotificationImpl.postViaApi(SlackNotificationImpl.java:192)
    at slacknotifications.SlackNotificationImpl.post(SlackNotificationImpl.java:152)
...

It seems to me that plugin require commons-codec version higher that teamcity bundled version. Attempt to up library version in teamcity leads to endless upgrade all builds agents.

[marvin-w]

This can be resolved by running the plugin in a different context.

[stijnvanbever]

This can be resolved by running the plugin in a different context.

Sorry to reply on this old bug. But can you explain how to run a plugin in a different context?
I'm facing with the same issue on TeamCity 10.0.4 (build 42538)