Update module helpers to avoid Python imports.

This avoids errors in creating Flask instances where there are import
errors in the module or package matching the import name.  Those runtime
errors will be apparent to the user soon enough, but tools which build
Flask instances meta-programmatically benefit from a Flask which does
not __import__.

flask/helpers.py

@@ -11,8 +11,10 @@
 
 from __future__ import with_statement
 
+import imp
 import os
 import sys
+import pkgutil
 import posixpath
 import mimetypes
 from time import time
@@ -492,14 +494,12 @@ def get_root_path(import_name):
 
     Not to be confused with the package path returned by :func:`find_package`.
     """
-    __import__(import_name)
-    try:
-        directory = os.path.dirname(sys.modules[import_name].__file__)
-        return os.path.abspath(directory)
-    except AttributeError:
-        # this is necessary in case we are running from the interactive
-        # python shell.  It will never be used for production code however
+    loader = pkgutil.get_loader(import_name)
+    if loader is None:
         return os.getcwd()
+    filepath = os.path.abspath(loader.get_filename(import_name))
+    # filepath for import_name.py for a module, or __init__.py for a package.
+    return os.path.dirname(filepath)
 
 
 def find_package(import_name):
@@ -510,16 +510,17 @@ def find_package(import_name):
     import the module.  The prefix is the path below which a UNIX like
     folder structure exists (lib, share etc.).
     """
-    __import__(import_name)
-    root_mod = sys.modules[import_name.split('.')[0]]
-    package_path = getattr(root_mod, '__file__', None)
-    if package_path is None:
+    root_mod_name = import_name.split('.')[0]
+    loader = pkgutil.get_loader(root_mod_name)
+    if loader is not None:
+        filename = loader.get_filename(root_mod_name)
+        package_path = os.path.abspath(os.path.dirname(filename))
+        # package_path ends with __init__.py for a package
+        if loader.is_package(root_mod_name):
+            package_path = os.path.dirname(package_path)
+    else:
         # support for the interactive python shell
         package_path = os.getcwd()
-    else:
-        package_path = os.path.abspath(os.path.dirname(package_path))
-    if hasattr(root_mod, '__path__'):
-        package_path = os.path.dirname(package_path)
 
     # leave the egg wrapper folder or the actual .egg on the filesystem
     test_package_path = package_path