Q:

Eclipse Plugin Dev: Unable to resolve dependencies

Based on this simple tutorial, I am trying to display pop-ups notifications, as part of the org.eclipse.mylyn.commons.ui dependency. So I have added this dependency to my plugin.xml as such:
Manifest-Version: 1.0
Bundle-ManifestVersion: 2
Bundle-Name: Roll and Scroll Recorder
Bundle-SymbolicName: ATF_Recorder_Plugin;singleton:=true
Bundle-Version: 0.0.502
Bundle-Activator: com.jcraft.eclipse.jcterm.JCTermPlugin
Require-Bundle: org.eclipse.ui,
 org.eclipse.core.runtime,
 com.jcraft.jsch;bundle-version="0.1.31",
 org.eclipse.core.resources;bundle-version="3.7.101",
 org.eclipse.jsch.core;bundle-version="1.1.300",
 com.jcraft.eclipse.jsch.core,
 org.eclipse.mylyn.commons.ui;bundle-version="3.6.1"
Bundle-ActivationPolicy: lazy
Bundle-RequiredExecutionEnvironment: JavaSE-1.6
Bundle-Vendor: OSEHRA

Additionally I clicked compute dependencies within my Feature project and now have this updated into my feature.xml file:
<requires>
  <import plugin="org.eclipse.ui"/>
  <import plugin="org.eclipse.core.runtime"/>
  <import plugin="com.jcraft.jsch" version="0.1.31" match="greaterOrEqual"/>
  <import plugin="org.eclipse.core.resources" version="3.7.101" match="greaterOrEqual"/>
  <import plugin="org.eclipse.jsch.core" version="1.1.300" match="greaterOrEqual"/>
  <import plugin="com.jcraft.eclipse.jsch.core"/>
  <import plugin="org.eclipse.mylyn.commons.ui" version="3.6.1" match="greaterOrEqual"/>
</requires>

However when I installed my custom plugin, and go to show it's view, the dependency is never being resolved:
java.lang.ClassNotFoundException: org.eclipse.mylyn.internal.provisional.commons.ui.AbstractNotificationPopup
at org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(BundleLoader.java:513)
at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:429)
at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:417)
at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.loadClass(DefaultClassLoader.java:107)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(Unknown Source)
at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.defineClass(DefaultClassLoader.java:188)
at org.eclipse.osgi.baseadaptor.loader.ClasspathManager.defineClassHoldingLock(ClasspathManager.java:626)
at org.eclipse.osgi.baseadaptor.loader.ClasspathManager.defineClass(ClasspathManager.java:601)
at org.eclipse.osgi.baseadaptor.loader.ClasspathManager.findClassImpl(ClasspathManager.java:562)
at org.eclipse.osgi.baseadaptor.loader.ClasspathManager.findLocalClassImpl(ClasspathManager.java:486)
at org.eclipse.osgi.baseadaptor.loader.ClasspathManager.findLocalClass(ClasspathManager.java:459)
at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.findLocalClass(DefaultClassLoader.java:216)
at org.eclipse.osgi.internal.loader.BundleLoader.findLocalClass(BundleLoader.java:400)
at org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(BundleLoader.java:476)
at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:429)
at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:417)
at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.loadClass(DefaultClassLoader.java:107)
at java.lang.ClassLoader.loadClass(Unknown Source)
at com.jcraft.eclipse.jcterm.JCTermView.createPartControl(JCTermView.java:189)
at org.eclipse.ui.internal.ViewReference.createPartHelper(ViewReference.java:375)
at org.eclipse.ui.internal.ViewReference.createPart(ViewReference.java:229)
at org.eclipse.ui.internal.WorkbenchPartReference.getPart(WorkbenchPartReference.java:595)
at org.eclipse.ui.internal.Perspective.showView(Perspective.java:2245)
...

A:

And the lesson from this question is
Don't ever use non-API classes, unless you don't care if your plug-in breaks in future versions.
I guess you have to build your plug-in twice, if you absolutely need backward compatibility.
But, since

you are targeting Indigo (3.7)
the bug, in the context of which the provisional packages became API, is Bug 360301
this bug fix was included in Mylyn 3.7

you are probably best of requiring org.eclipse.mylyn.commons.ui, version 3.7 and later.
Since you are using Eclipse 3.6 for development, you will have to set up a target platform including a 3.7 installation.

