update setup.py to retry without building extensions if first attempt fails

setup.py

@@ -12,10 +12,10 @@ from setuptools import setup, find_packages
 repo = os.path.dirname(__file__)
 version = write_vers(vers_file='wetb/__init__.py', repo=repo, skip_chars=1)
 
-#try:
+# try:
 #    from pypandoc import convert_file
 #    read_md = lambda f: convert_file(f, 'rst', format='md')
-#except ImportError:
+# except ImportError:
 #    print("warning: pypandoc module not found, could not convert Markdown to RST")
 #    read_md = lambda f: open(f, 'r').read()
 with open("README.md", "r") as fh:
@@ -26,10 +26,12 @@ from distutils.extension import Extension
 from Cython.Distutils import build_ext
 
 
-def setup_package():
-
-    ex_info = [('wetb.fatigue_tools.rainflowcounting', ['pair_range', 'peak_trough', 'rainflowcount_astm']),
-               ('wetb.signal.filters', ['cy_filters'])]
+def setup_package(build_ext=True):
+    if build_ext:
+        ex_info = [('wetb.fatigue_tools.rainflowcounting', ['pair_range', 'peak_trough', 'rainflowcount_astm']),
+                   ('wetb.signal.filters', ['cy_filters'])]
+    else:
+        ex_info = []
     extlist = [Extension('%s.%s' % (module, n),
                          [os.path.join(module.replace(".", "/"), n) + '.pyx'],
                          include_dirs=[np.get_include()]) for module, names in ex_info for n in names]
@@ -40,7 +42,7 @@ def setup_package():
                         'tables',
                         'pytest',
                         'pytest-cov',
-#                        'blosc', # gives an error - has to be pre-installed
+                        #                        'blosc', # gives an error - has to be pre-installed
                         'pbr',
                         'paramiko',
                         'scipy',
@@ -69,4 +71,9 @@ def setup_package():
 
 
 if __name__ == "__main__":
-    setup_package()
+    try:
+        setup_package()
+    except:
+        setup_package(False)
+        raise Warning(
+            "WETB installed, but building extensions failed (i.e. it falls back on the slower pure python implementions)")