Handle cases of packages with no files

For packages installed in 'pip editable' or 'setup.py develop' mode, the
`package` dict has no "files" key, so this fails with a KeyError. (I am
assuming that some version of pip returned a `package` dict with "files"
present but set to `None` or somesuch, so I have left the "`or []`" even
though it seems like a simple mistake.)

Author: wcooley

pip_check_reqs/find_extra_reqs.py

@@ -24,7 +24,7 @@ def find_extra_reqs(options):
     for package in search_packages_info(all_pkgs):
         log.debug('installed package: %s (at %s)', package['name'],
             package['location'])
-        for f in package['files'] or []:
+        for f in package.get('files', []) or []:
             path = os.path.realpath(os.path.join(package['location'], f))
             installed_files[path] = package['name']
             package_path = common.is_package_file(path)

pip_check_reqs/find_missing_reqs.py

@@ -26,7 +26,7 @@ def find_missing_reqs(options):
     for package in search_packages_info(all_pkgs):
         log.debug('installed package: %s (at %s)', package['name'],
             package['location'])
-        for file in package['files'] or []:
+        for file in package.get('files', []) or []:
             path = os.path.realpath(os.path.join(package['location'], file))
             installed_files[path] = package['name']
             package_path = common.is_package_file(path)