Strip out all -e flags when processing requirements file

Previously, there were various with installing editable packages in
different python / pip versions.
serverless#240

This adds logic to strip out all '-e' editable flags from the
requirements.txt file and issues a warning to the CLI.

fixes serverless#240

lib/pip.js

@@ -69,7 +69,8 @@ function generateRequirementsFile(
     filterRequirementsFile(
       path.join(servicePath, '.serverless/requirements.txt'),
       targetFile,
-      options
+      options,
+      serverless
     );
     serverless.cli.log(
       `Parsed requirements.txt from pyproject.toml in ${targetFile}...`
@@ -81,13 +82,14 @@ function generateRequirementsFile(
     filterRequirementsFile(
       path.join(servicePath, '.serverless/requirements.txt'),
       targetFile,
-      options
+      options,
+      serverless
     );
     serverless.cli.log(
       `Parsed requirements.txt from Pipfile in ${targetFile}...`
     );
   } else {
-    filterRequirementsFile(requirementsPath, targetFile, options);
+    filterRequirementsFile(requirementsPath, targetFile, options, serverless);
     serverless.cli.log(
       `Generated requirements from ${requirementsPath} in ${targetFile}...`
     );
@@ -378,7 +380,7 @@ function getRequirements(source) {
  * @param {string} target requirements where results are written
  * @param {Object} options
  */
-function filterRequirementsFile(source, target, options) {
+function filterRequirementsFile(source, target, options, serverless) {
   const noDeploy = new Set(options.noDeploy || []);
   const requirements = getRequirements(source);
   var prepend = [];
@@ -395,7 +397,15 @@ function filterRequirementsFile(source, target, options) {
       req.startsWith('-i') ||
       req.startsWith('-r')
     ) {
-      // If we have options (prefixed with --) keep them for later
+      if (req.startsWith('-e')) {
+        // strip out editable flags
+        // not required inside final archive and avoids pip bugs
+        // see https://github.com/UnitedIncome/serverless-python-requirements/issues/240
+        req = req.split('-e')[1].trim();
+        serverless.cli.log(`Warning: Stripping -e flag from requirement ${req}`);
+      }
+
+      // Keep options for later
       prepend.push(req);
       return false;
     } else if (req === '') {