scanpypi: ignore empty elements in package requirements

Depending on how setup.py reads requirements files empty elements can occur.
This patch takes care, that such elements will be ignored and don't crash
the scanpypi script.

Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
Tested-by: Matt Weber <matthew.weber@rockwellcollins.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

utils/scanpypi

@@ -295,7 +295,8 @@ class BuildrootPackage():
                         for req in self.pkg_req]
 
         # get rid of commented lines and also strip the package strings
-        self.pkg_req = [item.strip() for item in self.pkg_req if item[0] != '#']
+        self.pkg_req = [item.strip() for item in self.pkg_req
+                        if len(item) > 0 and item[0] != '#']
 
         req_not_found = self.pkg_req
         self.pkg_req = map(pkg_buildroot_name, self.pkg_req)