fix crash during module generation when '%' character is used in description

[boegel]

This occurs with EasyBuild v3.2.0 when installing bzip2.

$ eb bzip2-1.0.6.eb
ERROR: Traceback (most recent call last):
  File "/vscmnt/gent_vulpix/_/user/data/gent/gvo000/gvo00002/vsc40023/easybuild_easy_installed/lib/python2.6/site-packages/easybuild_framework-3.3.0.dev0-py2.7.egg/easybuild/main.py", line 117, in build_and_install_software
    (ec_res['success'], app_log, err) = build_and_install_one(ec, init_env)
  File "/user/data/gent/vsc400/vsc40023/easybuild_easy_installed/lib/python2.7/site-packages/easybuild_framework-3.3.0.dev0-py2.7.egg/easybuild/framework/easyblock.py", line 2531, in build_and_install_one
    result = app.run_all_steps(run_test_cases=run_test_cases)
  File "/user/data/gent/vsc400/vsc40023/easybuild_easy_installed/lib/python2.7/site-packages/easybuild_framework-3.3.0.dev0-py2.7.egg/easybuild/framework/easyblock.py", line 2447, in run_all_steps
    self.run_step(step_name, step_methods)
  File "/user/data/gent/vsc400/vsc40023/easybuild_easy_installed/lib/python2.7/site-packages/easybuild_framework-3.3.0.dev0-py2.7.egg/easybuild/framework/easyblock.py", line 2325, in run_step
    step_method(self)()
  File "/user/data/gent/vsc400/vsc40023/easybuild_easy_installed/lib/python2.7/site-packages/easybuild_easyblocks-3.2.0-py2.7.egg/easybuild/easyblocks/b/bzip2.py", line 110, in sanity_check_step
    super(EB_bzip2, self).sanity_check_step(custom_paths=custom_paths)
  File "/user/data/gent/vsc400/vsc40023/easybuild_easy_installed/lib/python2.7/site-packages/easybuild_framework-3.3.0.dev0-py2.7.egg/easybuild/framework/easyblock.py", line 1844, in sanity_check_step
    self._sanity_check_step(*args, **kwargs)
  File "/user/data/gent/vsc400/vsc40023/easybuild_easy_installed/lib/python2.7/site-packages/easybuild_framework-3.3.0.dev0-py2.7.egg/easybuild/framework/easyblock.py", line 2041, in _sanity_check_step
    fake_mod_data = self.load_fake_module(purge=True)
  File "/user/data/gent/vsc400/vsc40023/easybuild_easy_installed/lib/python2.7/site-packages/easybuild_framework-3.3.0.dev0-py2.7.egg/easybuild/framework/easyblock.py", line 1211, in load_fake_module
    fake_mod_path = self.make_module_step(fake=True)
  File "/user/data/gent/vsc400/vsc40023/easybuild_easy_installed/lib/python2.7/site-packages/easybuild_framework-3.3.0.dev0-py2.7.egg/easybuild/framework/easyblock.py", line 2149, in make_module_step
    txt += self.make_module_description()
  File "/user/data/gent/vsc400/vsc40023/easybuild_easy_installed/lib/python2.7/site-packages/easybuild_framework-3.3.0.dev0-py2.7.egg/easybuild/framework/easyblock.py", line 1000, in make_module_description
    return self.module_generator.get_description()
  File "/user/data/gent/vsc400/vsc40023/easybuild_easy_installed/lib/python2.7/site-packages/easybuild_framework-3.3.0.dev0-py2.7.egg/easybuild/tools/module_generator.py", line 697, in get_description
    'homepage': self.app.cfg['homepage'],
ValueError: unsupported format character 't' (0x74) at index 150

(this slipped through the cracks via #2113, cc @geimer)

[boegel]

@wpoely86 please review?

[boegel]

Thanks for the review @wpoely86!