[python-client] Modify python templates to resolve linting errors (#6839)

The linting results for the generated samples are as follows
where the first number is the BEFORE and the second is AFTER.

pyclient            7714 vs. 120
pyclient3           7717 vs. 120
pyclient3-asyncio   7584 vs. 120
pyclient-tornado    7633 vs. 120
pyclient3-tornado   7633 vs. 120

For the complete details please see the following gist.
https://gist.github.com/kenjones-cisco/2eb69a7e8db75e9fd53789f01570d9f2

Enforces linting for python clients by running flake8 for the generated
python client.

Author: kenjones-cisco

modules/swagger-codegen/src/main/java/io/swagger/codegen/languages/PythonClientCodegen.java

@@ -67,6 +67,7 @@ public PythonClientCodegen() {
         languageSpecificPrimitives.add("int");
         languageSpecificPrimitives.add("float");
         languageSpecificPrimitives.add("list");
+        languageSpecificPrimitives.add("dict");
         languageSpecificPrimitives.add("bool");
         languageSpecificPrimitives.add("str");
         languageSpecificPrimitives.add("datetime");
@@ -189,21 +190,16 @@ public void processOpts() {
             setPackageUrl((String) additionalProperties.get(PACKAGE_URL));
         }
 
-        String swaggerFolder = packageName;
-
-        modelPackage = swaggerFolder + File.separatorChar + "models";
-        apiPackage = swaggerFolder + File.separatorChar + "apis";
-
         supportingFiles.add(new SupportingFile("README.mustache", "", "README.md"));
 
         supportingFiles.add(new SupportingFile("tox.mustache", "", "tox.ini"));
         supportingFiles.add(new SupportingFile("test-requirements.mustache", "", "test-requirements.txt"));
         supportingFiles.add(new SupportingFile("requirements.mustache", "", "requirements.txt"));
 
-        supportingFiles.add(new SupportingFile("configuration.mustache", swaggerFolder, "configuration.py"));
-        supportingFiles.add(new SupportingFile("__init__package.mustache", swaggerFolder, "__init__.py"));
-        supportingFiles.add(new SupportingFile("__init__model.mustache", modelPackage, "__init__.py"));
-        supportingFiles.add(new SupportingFile("__init__api.mustache", apiPackage, "__init__.py"));
+        supportingFiles.add(new SupportingFile("configuration.mustache", packageName, "configuration.py"));
+        supportingFiles.add(new SupportingFile("__init__package.mustache", packageName, "__init__.py"));
+        supportingFiles.add(new SupportingFile("__init__model.mustache", packageName + File.separatorChar + modelPackage, "__init__.py"));
+        supportingFiles.add(new SupportingFile("__init__api.mustache", packageName + File.separatorChar + apiPackage, "__init__.py"));
 
         if(Boolean.FALSE.equals(excludeTests)) {
             supportingFiles.add(new SupportingFile("__init__test.mustache", testFolder, "__init__.py"));
@@ -212,23 +208,42 @@ public void processOpts() {
         supportingFiles.add(new SupportingFile("gitignore.mustache", "", ".gitignore"));
         supportingFiles.add(new SupportingFile("travis.mustache", "", ".travis.yml"));
         supportingFiles.add(new SupportingFile("setup.mustache", "", "setup.py"));
-        supportingFiles.add(new SupportingFile("api_client.mustache", swaggerFolder, "api_client.py"));
+        supportingFiles.add(new SupportingFile("api_client.mustache", packageName, "api_client.py"));
 
         if ("asyncio".equals(getLibrary())) {
-            supportingFiles.add(new SupportingFile("asyncio/rest.mustache", swaggerFolder, "rest.py"));
+            supportingFiles.add(new SupportingFile("asyncio/rest.mustache", packageName, "rest.py"));
             additionalProperties.put("asyncio", "true");
         } else if ("tornado".equals(getLibrary())) {
-            supportingFiles.add(new SupportingFile("tornado/rest.mustache", swaggerFolder, "rest.py"));
+            supportingFiles.add(new SupportingFile("tornado/rest.mustache", packageName, "rest.py"));
             additionalProperties.put("tornado", "true");
         } else {
-            supportingFiles.add(new SupportingFile("rest.mustache", swaggerFolder, "rest.py"));
+            supportingFiles.add(new SupportingFile("rest.mustache", packageName, "rest.py"));
         }
+
+        modelPackage = packageName + "." + modelPackage;
+        apiPackage = packageName + "." + apiPackage;
+
     }
 
     private static String dropDots(String str) {
         return str.replaceAll("\\.", "_");
     }
 
+    @Override
+    public String toModelImport(String name) {
+        String modelImport;
+        if (StringUtils.startsWithAny(name,"import", "from")) {
+            modelImport = name;
+        } else {
+            modelImport = "from ";
+            if (!"".equals(modelPackage())) {
+                modelImport += modelPackage() + ".";
+            }
+            modelImport += toModelFilename(name)+ " import " + name;
+        }
+        return modelImport;
+    }
+
     @Override
     public Map<String, Object> postProcessModels(Map<String, Object> objs) {
         // process enum in models

modules/swagger-codegen/src/main/resources/flaskConnexion/model.mustache

@@ -6,7 +6,7 @@ from datetime import date, datetime  # noqa: F401
 from typing import List, Dict  # noqa: F401
 
 from {{modelPackage}}.base_model_ import Model
-{{#imports}}{{import}}  # noqa: E501
+{{#imports}}{{import}}  # noqa: F401,E501
 {{/imports}}
 from {{packageName}} import util
 
@@ -94,15 +94,15 @@ class {{classname}}(Model):
         if not set({{{name}}}).issubset(set(allowed_values)):
             raise ValueError(
                 "Invalid values for `{{{name}}}` [{0}], must be a subset of [{1}]"  # noqa: E501
-                .format(", ".join(map(str, set({{{name}}})-set(allowed_values))),  # noqa: E501
+                .format(", ".join(map(str, set({{{name}}}) - set(allowed_values))),  # noqa: E501
                         ", ".join(map(str, allowed_values)))
             )
 {{/isListContainer}}
 {{#isMapContainer}}
         if not set({{{name}}}.keys()).issubset(set(allowed_values)):
             raise ValueError(
                 "Invalid keys in `{{{name}}}` [{0}], must be a subset of [{1}]"  # noqa: E501
-                .format(", ".join(map(str, set({{{name}}}.keys())-set(allowed_values))),  # noqa: E501
+                .format(", ".join(map(str, set({{{name}}}.keys()) - set(allowed_values))),  # noqa: E501
                         ", ".join(map(str, allowed_values)))
             )
 {{/isMapContainer}}

modules/swagger-codegen/src/main/resources/python/__init__api.mustache

@@ -1,8 +1,7 @@
 from __future__ import absolute_import
 
+# flake8: noqa
+
 # import apis into api package
-{{#apiInfo}}
-{{#apis}}
-from .{{classVarName}} import {{classname}}
-{{/apis}}
-{{/apiInfo}}
+{{#apiInfo}}{{#apis}}from {{apiPackage}}.{{classVarName}} import {{classname}}
+{{/apis}}{{/apiInfo}}

modules/swagger-codegen/src/main/resources/python/__init__model.mustache

@@ -1,9 +1,10 @@
 # coding: utf-8
 
+# flake8: noqa
 {{>partial_header}}
 
 from __future__ import absolute_import
 
 # import models into model package
-{{#models}}{{#model}}from .{{classFilename}} import {{classname}}{{/model}}
+{{#models}}{{#model}}from {{modelPackage}}.{{classFilename}} import {{classname}}{{/model}}
 {{/models}}

modules/swagger-codegen/src/main/resources/python/__init__package.mustache

@@ -1,16 +1,17 @@
 # coding: utf-8
 
+# flake8: noqa
+
 {{>partial_header}}
 
 from __future__ import absolute_import
 
-# import models into sdk package
-{{#models}}{{#model}}from .models.{{classFilename}} import {{classname}}
-{{/model}}{{/models}}
 # import apis into sdk package
-{{#apiInfo}}{{#apis}}from .apis.{{classVarName}} import {{classname}}
+{{#apiInfo}}{{#apis}}from {{apiPackage}}.{{classVarName}} import {{classname}}
 {{/apis}}{{/apiInfo}}
 # import ApiClient
-from .api_client import ApiClient
-
-from .configuration import Configuration
+from {{packageName}}.api_client import ApiClient
+from {{packageName}}.configuration import Configuration
+# import models into sdk package
+{{#models}}{{#model}}from {{modelPackage}}.{{classFilename}} import {{classname}}
+{{/model}}{{/models}}