EDIT

During an export that was interrupted by a restarting CdmServer I got the below error.

The message is difficult to understand for ordinary users. We should make simple, e.g. "Server seems to be not available. Please retry later".

possibly duplicates (although different HTTP response code) #6355

Could not access HTTP invoker remote service at [...] nested exception is ... response code 502 .... with error trace below .....
login : 
editor version : 4.8.0.201706150749
server :  ()
schema version : 
os : Windows Server 2012 R2 6.3 amd64
java : 1.8.0_121
org.springframework.remoting.RemoteAccessException: Could not access HTTP invoker remote service at [http://test.e-taxonomy.eu:80/cdmserver/caryo_spp/remoting/io.service]; nested exception is org.apache.http.NoHttpResponseException: Did not receive successful HTTP response: status code = 502, status message = [Proxy Error]
    at org.springframework.remoting.httpinvoker.HttpInvokerClientInterceptor.convertHttpInvokerAccessException(HttpInvokerClientInterceptor.java:216)
    at org.springframework.remoting.httpinvoker.HttpInvokerClientInterceptor.invoke(HttpInvokerClientInterceptor.java:147)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:208)
    at com.sun.proxy.$Proxy48.export(Unknown Source)
    at eu.etaxonomy.taxeditor.io.ExportManager$3.run(ExportManager.java:293)
    at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)
Caused by: org.apache.http.NoHttpResponseException: Did not receive successful HTTP response: status code = 502, status message = [Proxy Error]
    at org.springframework.remoting.httpinvoker.HttpComponentsHttpInvokerRequestExecutor.validateResponse(HttpComponentsHttpInvokerRequestExecutor.java:357)
    at org.springframework.remoting.httpinvoker.HttpComponentsHttpInvokerRequestExecutor.doExecuteRequest(HttpComponentsHttpInvokerRequestExecutor.java:230)
    at eu.etaxonomy.taxeditor.service.CdmServiceRequestExecutor.doExecuteRequest(CdmServiceRequestExecutor.java:61)
    at org.springframework.remoting.httpinvoker.AbstractHttpInvokerRequestExecutor.executeRequest(AbstractHttpInvokerRequestExecutor.java:138)
    at org.springframework.remoting.httpinvoker.HttpInvokerClientInterceptor.executeRequest(HttpInvokerClientInterceptor.java:194)
    at org.springframework.remoting.httpinvoker.HttpInvokerClientInterceptor.executeRequest(HttpInvokerClientInterceptor.java:176)
    at org.springframework.remoting.httpinvoker.HttpInvokerClientInterceptor.invoke(HttpInvokerClientInterceptor.java:144)
    ... 5 more