all: make newer pycodestyle happy

Apparently the "two empty lines" rule is now stricter.

fdroidserver/metadata.py

@@ -218,6 +218,7 @@ class App():
             else:
                 self.set_field(f, v)
 
+
 TYPE_UNKNOWN = 0
 TYPE_OBSOLETE = 1
 TYPE_STRING = 2
@@ -370,6 +371,7 @@ class Build():
         for f, v in d.items():
             self.set_flag(f, v)
 
+
 flagtypes = {
     'extlibs': TYPE_LIST,
     'srclibs': TYPE_LIST,
@@ -429,6 +431,7 @@ class FieldValidator():
                 warn_or_exception("'%s' is not a valid %s in %s. Regex pattern: %s"
                                   % (v, self.name, appid, self.matching))
 
+
 # Generic value types
 valuetypes = {
     FieldValidator("Integer",
@@ -819,6 +822,7 @@ def read_metadata(xref=True):
 
     return apps
 
+
 # Port legacy ';' separators
 list_sep = re.compile(r'[,;]')