Fix #99, continue if a local package isn't exists

Signed-off-by: Xiaochao Dong (@damnever) <the.xcdong@gmail.com>

.github/workflows/ci.yml

@@ -7,10 +7,11 @@ jobs:
       matrix:
         python-version:
           - "2.7"
-          - "3.5"
           - "3.6"
           - "3.7"
           - "3.8"
+          - "3.9"
+          - "3.10"
     name: Python ${{ matrix.python-version }}
     steps:
       - uses: actions/checkout@v1

README.md

@@ -54,6 +54,8 @@ pip install git+https://github.com/damnever/pigar.git@[master or other branch] -
 
     If the requirements.txt is overwritten, ``pigar`` will show the difference between the old and the new.
 
+    **NOTE**, `pigar` will search the packages in local environment first, then it will search missing packages in PyPI.
+
 - If you do not know the import name that belongs to a specific package (more generally, does `Import Error: xxx` drive you crazy?), such as `bs4` which may come from `beautifulsoup4` or `MySQLdb` which could come from `MySQL_Python`, try searching for it:
 
     ```
@@ -81,6 +83,16 @@ pip install git+https://github.com/damnever/pigar.git@[master or other branch] -
 
 ### FAQ
 
+<details>
+  <summary>
+  Is `pigar` a dependency management tool?
+  </summary>
+
+**No.** I've thought about it many times, but there is too much dirty work to be done to make `pigar`'s way reliable.
+
+I like the way `pigar` does the job, but sadly, `pigar` does a bad job of managing dependencies, `pigar` is more like a tool to assist an old project to migrate to a new development workflow.
+</details>
+
 <details>
   <summary>
   (1) Why `pigar` generates multiple packages for same import name?

pigar/parser.py

@@ -298,7 +298,7 @@ def _search_path(path):
                     line = line.strip()
                     if line != '.':
                         dev_dir = line
-            if not dev_dir:
+            if not dev_dir or not pathlib.exists(dev_dir):
                 continue
             # Egg info path.
             info_dir = [