add requirements.txt

CONTRIBUTING.md

@@ -26,9 +26,12 @@ Here's the process to make changes to the codebase:
 2. Review [open pull requests](https://github.com/spdx/tools-python/pulls) before committing time to a substantial
    revision. Work along similar lines may already be in progress.
 
-3. Create a new branch:
+3. Create a new branch and set up environment:
    ```sh
    git checkout -b fix-or-improve-something
+   python -m venv ./venv
+   ./venv/bin/activate
+   pip install -r requirements.txt
    ```
 4. Make some changes and commit them to the branch:
    ```sh

requirements.txt

@@ -0,0 +1,7 @@
+click
+ply
+pytest
+pyyaml
+rdflib
+uritools
+xmltodict

spdx/parsers/parse_anything.py

@@ -21,10 +21,13 @@
 from spdx.parsers.builderexceptions import FileTypeError
 
 
-def parse_file(fn):
+def parse_file(fn, encoding="utf-8"):
+    in_mode = "r"
     builder_module = jsonyamlxmlbuilders
     read_data = False
     if fn.endswith(".rdf") or fn.endswith(".rdf.xml"):
+        in_mode = "rb"
+        encoding = None
         parsing_module = rdf
         builder_module = rdfbuilders
     elif fn.endswith(".tag") or fn.endswith(".spdx"):
@@ -43,7 +46,7 @@ def parse_file(fn):
     p = parsing_module.Parser(builder_module.Builder(), StandardLogger())
     if hasattr(p, "build"):
         p.build()
-    with open(fn) as f:
+    with open(fn, in_mode, encoding=encoding) as f:
         if read_data:
             data = f.read()
             return p.parse(data)

spdx/writers/write_anything.py

@@ -23,6 +23,7 @@ def write_file(doc, fn, validate=True, encoding="utf-8"):
     if fn.endswith(".rdf") or fn.endswith(".rdf.xml"):
         writer_module = rdf
         out_mode = "wb"
+        encoding = None
     elif fn.endswith(".tag") or fn.endswith(".spdx"):
         writer_module = tagvalue
     elif fn.endswith(".json"):