Enforce PEP 257 conventions in ftplib.py (GH-15604)

-`"""` over `'''`
-no blank line either before or after the docstring.
-place the closing quotes on a line by themselves

Lib/ftplib.py

@@ -72,7 +72,6 @@ B_CRLF = b'\r\n'
 
 # The class itself
 class FTP:
-
     '''An FTP client class.
 
     To create a connection, call the class using these arguments:
@@ -105,12 +104,13 @@ class FTP:
     passiveserver = 1
     encoding = "latin-1"
 
-    # Initialization method (called by class instantiation).
-    # Initialize host to localhost, port to standard ftp port
-    # Optional arguments are host (for connect()),
-    # and user, passwd, acct (for login())
     def __init__(self, host='', user='', passwd='', acct='',
                  timeout=_GLOBAL_DEFAULT_TIMEOUT, source_address=None):
+        """Initialization method (called by class instantiation).
+        Initialize host to localhost, port to standard ftp port.
+        Optional arguments are host (for connect()),
+        and user, passwd, acct (for login()).
+        """
         self.source_address = source_address
         self.timeout = timeout
         if host:
@@ -823,7 +823,6 @@ def parse227(resp):
     '''Parse the '227' response for a PASV request.
     Raises error_proto if it does not contain '(h1,h2,h3,h4,p1,p2)'
     Return ('host.addr.as.numbers', port#) tuple.'''
-
     if resp[:3] != '227':
         raise error_reply(resp)
     global _227_re
@@ -843,7 +842,6 @@ def parse229(resp, peer):
     '''Parse the '229' response for an EPSV request.
     Raises error_proto if it does not contain '(|||port|)'
     Return ('host.addr.as.numbers', port#) tuple.'''
-
     if resp[:3] != '229':
         raise error_reply(resp)
     left = resp.find('(')
@@ -865,7 +863,6 @@ def parse257(resp):
     '''Parse the '257' response for a MKD or PWD request.
     This is a response to a MKD or PWD request: a directory name.
     Returns the directoryname in the 257 reply.'''
-
     if resp[:3] != '257':
         raise error_reply(resp)
     if resp[3:5] != ' "':