Add system's requirements.txt, enforce flake8 linter

Fix style issues in functional tests.

system/t11_package/search.py

@@ -1,12 +1,16 @@
 from lib import BaseTest
 
 
+def sortLines(_, s):
+    return "\n".join(sorted(s.split("\n")))
+
+
 class SearchPackage1Test(BaseTest):
     """
     search package: regular search
     """
     fixtureDB = True
-    outputMatchPrepare = lambda _, s: "\n".join(sorted(s.split("\n")))
+    outputMatchPrepare = sortLines
     runCmd = "aptly package search '$$Architecture (i386), Name (% *-dev)'"
 
 
@@ -31,7 +35,7 @@ class SearchPackage4Test(BaseTest):
     search package: by dependency
     """
     fixtureDB = True
-    outputMatchPrepare = lambda _, s: "\n".join(sorted(s.split("\n")))
+    outputMatchPrepare = sortLines
     runCmd = "aptly package search coreutils"
 
 
@@ -40,13 +44,14 @@ class SearchPackage5Test(BaseTest):
     search package: with format
     """
     fixtureDB = True
-    outputMatchPrepare = lambda _, s: "\n".join(sorted(s.split("\n")))
+    outputMatchPrepare = sortLines
     runCmd = "aptly package search -format='{{.Package}}#{{.Version}}' '$$Architecture (i386), Name (% *-dev)'"
 
+
 class SearchPackage6Test(BaseTest):
     """
     search package: no query
     """
     fixtureDB = True
-    outputMatchPrepare = lambda _, s: "\n".join(sorted(s.split("\n")))
+    outputMatchPrepare = sortLines
     runCmd = "aptly package search"