Use relative paths when looking for python paths

Not only simplifies the code but is also the obviously correct way
which i should have used from the start.

Author: Micket

easybuild/framework/easyblock.py

@@ -1439,10 +1439,9 @@ def make_module_extra(self, altroot=None, altversion=None):
             lines.append(self.module_generator.append_paths(key, value, allow_abs=self.cfg['allow_append_abs_path']))
 
         # Add automatic PYTHONPATH or EBPYTHONPREFIXES if they aren't already present and python paths exist
-        if not os.path.isfile(f'{self.installdir}/bin/python'):  # only needed when not a base python installation
-            python_paths = [os.path.relpath(path, self.installdir)
-                            for path in glob.glob(f'{self.installdir}/lib/python*/site-packages')
-                            if re.match(self.installdir + r'/lib/python\d+\.\d+/site-packages', path)]
+        if not os.path.isfile(os.path.join(self.installdir, 'bin/python')):  # only needed when not a python install
+            python_paths = [path for path in glob.glob('lib/python*/site-packages', root_dir=self.installdir)
+                            if re.match(r'lib/python\d+\.\d+/site-packages', path]
 
             runtime_deps = [dep['name'] for dep in self.cfg.dependencies(runtime_only=True)]
             use_ebpythonprefixes = 'Python' in runtime_deps and \