title: issubclass() returns False on the same class imported from different paths
body: <p>The intention was to implement some sort of plugin framework, where plugins are subclasses (i.e. B) of the same base class (i.e. A). The base class is loaded with standard import, whereas subclasses are loaded with imp.load_module() from the path of a well-known package (i.e. pkg).</p>
  
  <pre><code>pkg/
      __init__.py
      mod1.py
          class A
      mod2.py
          class B(pkg.mod1.A)
  </code></pre>
  
  <p>This worked fine with <em>real</em> subclasses, i.e.,</p>
  
  <pre><code># test_1.py
  import pkg
  from pkg import mod1
  import imp
  tup = imp.find_module('mod2', pkg.__path__)
  mod2 = imp.load_module('mod2', tup[0], tup[1], tup[2])
  print(issubclass(mod2.B, mod1.A)) # True
  </code></pre>
  
  <p>But the problem came when testing the base class itself,</p>
  
  <pre><code># test_2.py
  import pkg
  from pkg import mod1
  import imp
  tup = imp.find_module('mod1', pkg.__path__)
  mod0 = imp.load_module('mod1', tup[0], tup[1], tup[2])
  print(issubclass(mod0.A, mod1.A)) # False
  </code></pre>
  
  <p>But mod0.A and mod1.A are actually the same class from the same file (pkg/mod1.py).</p>
  
  <p>This issue appears in both python 2.7 and 3.2.</p>
  
  <p>Now the question is two-fold, a) Is it an expected feature or a bug of issubclass(), and b) How to get rid of this without changing contents of pkg?</p>