Remove import of preamble to quiet pyflakes.

We don't really need preamble any more in these scripts, because
these scripts are run inside tox environments which properly
install Twisted in a virtualenv with the correct paths set up.

These scripts are not distributed as part of Twisted, but are used
during the Twisted release process.

bin/admin/build-apidocs

@@ -6,15 +6,7 @@
 # This script is not meant to be distributed to users of Twisted.
 # It is only for use in making upstream Twisted releases.
 
-import sys, os
-extra = os.path.join(os.path.dirname(os.path.dirname(sys.argv[0])), "src")
-sys.path.insert(0, extra)
-try:
-    import _preamble
-except ImportError:
-    pass
-sys.path.remove(extra)
-
+import sys
 from twisted.python._release import BuildAPIDocsScript
 
 BuildAPIDocsScript().main(sys.argv[1:])

bin/admin/build-docs

@@ -6,15 +6,7 @@
 # This script is not meant to be distributed to users of Twisted.
 # It is only for use in making upstream Twisted releases.
 
-import sys, os
-extra = os.path.join(os.path.dirname(os.path.dirname(sys.argv[0])), "src")
-sys.path.insert(0, extra)
-try:
-    import _preamble
-except ImportError:
-    pass
-sys.path.remove(extra)
-
+import sys
 from twisted.python._release import SphinxBuilder
 
 SphinxBuilder().main(sys.argv[1:])

bin/admin/check-topfile

@@ -8,15 +8,7 @@ Check that the current commits since branching have a topfile.
 
 from __future__ import absolute_import, division, print_function
 
-import sys, os
-extra = os.path.dirname(os.path.dirname(sys.argv[0]))
-sys.path.insert(0, extra)
-try:
-    import _preamble
-except ImportError:
-    pass
-sys.path.remove(extra)
-
+import sys
 from twisted.python._release import CheckTopfileScript
 
 CheckTopfileScript(print).main(sys.argv[1:])