Revert "Use resources loader to handle non-filesystem situations (#120)"

This reverts commit a9ab4b3.

Author: Lukasa

certifi/core.py

@@ -6,40 +6,25 @@
 
 This module returns the installation location of cacert.pem or its contents.
 """
-import importlib
 import os
 
 try:
-    import importlib.resources
-    # Defeat lazy module importers.
-    importlib.resources.open_binary
-    _HAVE_RESOURCE_READER = True
+    from importlib.resources import read_text
 except ImportError:
-    _HAVE_RESOURCE_READER = False
-
-try:
-    import pkg_resources
-    # Defeat lazy module importers.
-    _HAVE_PKG_RESOURCES = True
-except ImportError:
-    _HAVE_PKG_RESOURCES = False
-
-_PACKAGE_NAME = "certifi"
-_CACERT_NAME = "cacert.pem"
+    # This fallback will work for Python versions prior to 3.7 that lack the
+    # importlib.resources module but relies on the existing `where` function
+    # so won't address issues with environments like PyOxidizer that don't set
+    # __file__ on modules.
+    def read_text(_module, _path, encoding="ascii"):
+        with open(where(), "r", encoding=encoding) as data:
+            return data.read()
 
 
 def where():
-    if _HAVE_PKG_RESOURCES:
-        return pkg_resources.resource_filename(_PACKAGE_NAME, _CACERT_NAME)
-    else:
-        mod = importlib.import_module(_PACKAGE_NAME)
-        path = os.path.dirname(mod.__file__)
-        return os.path.join(path, _CACERT_NAME)
+    f = os.path.dirname(__file__)
+
+    return os.path.join(f, "cacert.pem")
 
 
 def contents():
-    if _HAVE_RESOURCE_READER:
-        return importlib.resources.read_text(_PACKAGE_NAME, _CACERT_NAME, encoding="ascii")
-    else:
-        with open(where(), "r", encoding="ascii") as data:
-            return data.read()
+    return read_text("certifi", "cacert.pem", encoding="ascii")