Import Python module with PyImport_ImportModuleEx

I'm learning Python and I try to use Python Markdown in a gedit plugin. Here's how my files are organized:

~/.gnome2/gedit/plugins/mytest.gedit-plugin
~/.gnome2/gedit/plugins/mytest/
~/.gnome2/gedit/plugins/mytest/__init__.py
~/.gnome2/gedit/plugins/mytest/markdown/
~/.gnome2/gedit/plugins/mytest/markdown/__init__.py
~/.gnome2/gedit/plugins/mytest/markdown/preprocessors.py
~/.gnome2/gedit/plugins/mytest/markdown/OTHER_FILES
~/.gnome2/gedit/plugins/mytest/markdown/extensions/
~/.gnome2/gedit/plugins/mytest/markdown/extensions/__init__.py
~/.gnome2/gedit/plugins/mytest/markdown/extensions/headerid.py
~/.gnome2/gedit/plugins/mytest/markdown/extensions/OTHER_FILES

Explication:

My file mytest.gedit-plugin only contains minimal code to declare the plugin:

[Gedit Plugin]
Loader=python
Module=mytest
IAge=2
Name=My test

My plugin has its own subfolder (mytest). The file mytest/__init__.py contains:

#!/usr/bin/python
# -*- coding: utf-8 -*-

import gedit
import markdown

class MyTestPlugin(gedit.Plugin):
    def __init__(self):
        gedit.Plugin.__init__(self)

    def activate(self, window):
        texte = "# Header 1 {#id}"
        print markdown.markdown(texte, extensions=['headerid'])

Finally, the folder mytest/markdown contains default Python Markdown code.

When I activate my plugin in gedit (Edit > Preferences > Plugins), output in the terminal is:

Traceback (most recent call last):
  File "/home/moi/.gnome2/gedit/plugins/mytest/__init__.py", line 5, in <module>
    import markdown
  File "/home/moi/.gnome2/gedit/plugins/mytest/markdown/__init__.py", line 161, in <module>
    import preprocessors
  File "/home/moi/.gnome2/gedit/plugins/mytest/markdown/preprocessors.py", line 11, in <module>
    import markdown
ImportError: No module named markdown

** (gedit:8790): WARNING **: Error loading plugin 'My test'

However, I successfully use Python Markdown outside gedit. For example, the following file works great when I run it in a terminal in the same location as the Python Markdown main folder:

#!/usr/bin/python
# -*- coding: utf-8 -*-

import markdown

texte = "# Header 1 {#id}"
print markdown.markdown(texte, extensions=['headerid'])

I found that if I change import markdown in Python Markdown files for import __init__ as markdown, I can use Python Markdown without its extensions (mytest/markdown/extensions/), but anyway, it still doesn't work with my example:

/home/moi/.gnome2/gedit/plugins/mytest/markdown/__init__.py:114: MarkdownWarning: Failed loading extension 'headerid' from 'markdown.extensions.headerid' or 'mdx_headerid'
  warnings.warn(text, MarkdownWarning)
<h1>Header 1 {#id}</h1>

So, my question is how could I modify import for extensions, or how could I install Python Markdown in a local emplacement (so in $HOME, without root access) to be able to use Python Markdown in a gedit plugin?

Thanks a lot.

Note: I think gedit uses PyImport_ImportModuleEx() to load plugins, so that's why I put it in the title of my question.

Edit 1: 2 details: no root installation and possible to modify Python Markdown files.

Edit 2: Extensions are loaded with the following code in mytest/markdown/__init__.py (about line 525):

# Setup the module names
ext_module = 'markdown.extensions'
module_name_new_style = '.'.join([ext_module, ext_name])
module_name_old_style = '_'.join(['mdx', ext_name])

# Try loading the extention first from one place, then another
try: # New style (markdown.extensons.<extension>)
    module = __import__(module_name_new_style, {}, {}, [ext_module])
except ImportError:
    try: # Old style (mdx.<extension>)
        module = __import__(module_name_old_style)
    except ImportError:
       message(WARN, "Failed loading extension '%s' from '%s' or '%s'"
           % (ext_name, module_name_new_style, module_name_old_style))
       # Return None so we don't try to initiate none-existant extension
       return None

Maybe there's a way to import with relative path. I'm really beginner with Python.

If you want to use markdown without modifying it then you're going to have to put it somewhere where the Python library expects it, such as in site-packages/. Otherwise, you will have to modify it to use relative imports instead of absolute imports.