Fix blank line issues reported by flake8

- E301 expected 1 blank line
- E302 expected 2 blank lines
- E303 too many blank lines
- E305 expected 2 blank lines after class or function definition
- E306 expected 1 blank line before a nested definition

Fixed automatically with autopep8:

  git ls-files | grep py$ | xargs autopep8 --in-place \
    --select E301,E302,E303,E305,E306

Manually fix issues in project.py caused by misuse of block comments.

Change-Id: Iee840fcaff48aae504ddac9c3e76d2acd484f6a9
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/254599
Reviewed-by: Mike Frysinger <vapier@google.com>
Tested-by: David Pursehouse <dpursehouse@collab.net>

platform_utils.py

@@ -92,6 +92,7 @@ class _FileDescriptorStreamsNonBlocking(FileDescriptorStreams):
   """
   class Stream(object):
     """ Encapsulates a file descriptor """
+
     def __init__(self, fd, dest, std_name):
       self.fd = fd
       self.dest = dest
@@ -125,6 +126,7 @@ class _FileDescriptorStreamsThreads(FileDescriptorStreams):
   non blocking I/O. This implementation requires creating threads issuing
   blocking read operations on file descriptors.
   """
+
   def __init__(self):
     super(_FileDescriptorStreamsThreads, self).__init__()
     # The queue is shared accross all threads so we can simulate the
@@ -144,12 +146,14 @@ class _FileDescriptorStreamsThreads(FileDescriptorStreams):
 
   class QueueItem(object):
     """ Item put in the shared queue """
+
     def __init__(self, stream, data):
       self.stream = stream
       self.data = data
 
   class Stream(object):
     """ Encapsulates a file descriptor """
+
     def __init__(self, fd, dest, std_name, queue):
       self.fd = fd
       self.dest = dest