JaCoCo can not instrument classes which is already instrumented by Jmockit

Here is what I have: 

1) Sonar 3.5 which uses JaCoCo as coverage tool. 

2) Jmockit lib to perform testing with use of mocks. 

3) Build process automized with maven.

• Jmockit seems to instrument classes it need.
• JaCoCo can not instrument classes which is already instrumented by Jmockit and spits out a HUGE amount of exceptions, saying that it's impossible to instrument class, which were already instrumented. However Sonar seems to have a valid output for such a scenario.
  So first question is: can I somehow suppress such an exceptions? It is really critical because the size of the log file on our CI system achieves 50Mb (!), which is not acceptable. A lot of free space is just eaten up by such a logs on our CI machine.

Here are the exceptions I've got:

java.lang.instrument.IllegalClassFormatException: Error while instrumenting class app/MyClass.Caused by: java.lang.IllegalStateException: Class app/MyClass is already instrumented.

Assuming that suppression of such an exceptions is impossible I investigated it a little bit and found out that JaCoCo (a tool, which Sonar uses and a tool, which can't instrument already instrumented classes) have such a mode as offline instrumentation (AFAIK Sonar neither support this offline instrumentation or can suppress such a warnings). This thing is designed to be used exactly for such a cases. So I tried to set up JaCoCo as a plugin in maven, but I failed to do this cause JaCoCo can't find some execution file. When I'm running mvn clean install the following error pops up:

[INFO] --- jacoco-maven-plugin:0.6.2.201302030002:report (report) @ webservice-mws --- 

[INFO] Skipping JaCoCo execution due to missing execution data file

解决方法：
在jacoco 中添加：

<groupId>org.jacoco</groupId><artifactId>jacoco-maven-plugin</artifactId><version>${jacoco.version}</version><configuration>  <excludes>      <exclude>com.cloud.generated.*</exclude>  </excludes>  <skip>${jacoco.skip.instrument}</skip></configuration><executions><execution><id>default-instrument</id><goals><goal>instrument</goal></goals></execution><execution><id>default-restore-instrumented-classes</id><goals><goal>restore-instrumented-classes</goal></goals></execution><execution><id>default-report</id><phase>prepare-package</phase><goals><goal>report</goal></goals></execution></executions></plugin>

不然只能使用  
Cobertura 插件，因为jacoco和 mock存在 很多不兼容的地方。