Drop support for Python 3.6 (#192)

Part of issue #190

- update .travis.yml - Drop support for Python 3.6 and LXML versions, that work only in Python 3.6 9 (and not in any later version)
- update README.md - Mark Python 3.7 as minimal supported version.
- update CHANGELOG.md - Python 3.6 support removal
- update requirements.txt - Upgrade to minimal LXML package that still works on Python 3.7
- update setup.py - Upgrade to minimal LXML package that still works on Python 3.7
- update setup.py - Update pipy language classifiers

Author: phanak-sap

.travis.yml

@@ -1,16 +1,12 @@
 dist: bionic 
 language: python
 python:
-  - "3.6"
   - "3.7"
   - "3.8"
   - "3.9"
   - "3.10.1"
 
 env:
-  - LXML_VERSION=3.7.3
-  - LXML_VERSION=3.8.0
-  - LXML_VERSION=4.0.0
   - LXML_VERSION=4.1.1  
   - LXML_VERSION=4.2.6
   - LXML_VERSION=4.3.5
@@ -21,34 +17,10 @@ env:
 
 jobs:
   exclude:
-    - python: 3.7
-      env: LXML_VERSION=3.7.3
-    - python: 3.7
-      env: LXML_VERSION=3.8.0
-    - python: 3.7
-      env: LXML_VERSION=4.0.0  
-    - python: 3.8
-      env: LXML_VERSION=3.7.3
-    - python: 3.8
-      env: LXML_VERSION=3.8.0
-    - python: 3.8
-      env: LXML_VERSION=4.0.0       
-    - python: 3.9
-      env: LXML_VERSION=3.7.3   
-    - python: 3.9
-      env: LXML_VERSION=3.8.0      
-    - python: 3.9
-      env: LXML_VERSION=4.0.0     
     - python: 3.9
       env: LXML_VERSION=4.1.1      
     - python: 3.9
       env: LXML_VERSION=4.2.6           
-    - python: 3.10.1
-      env: LXML_VERSION=3.7.3
-    - python: 3.10.1
-      env: LXML_VERSION=3.8.0
-    - python: 3.10.1
-      env: LXML_VERSION=4.0.0     
     - python: 3.10.1
       env: LXML_VERSION=4.1.1
     - python: 3.10.1

CHANGELOG.md

@@ -10,6 +10,9 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Fixed
 - Fix Edm.Binary literal representation - Daniel Balko
 
+### Removed
+- Python 3.6 (after its EOL) is no longer supported by pyodata. Python 3.7 is now minimal supported version.
+
 ## [1.7.1]
 
 ### Fixed

README.md

@@ -18,7 +18,7 @@ details.
 
 ## Requirements
 
-- [Python >= 3.6](https://www.python.org/downloads/release/python-368/)
+- [Python >= 3.7](https://www.python.org/downloads/)
 
 ## Download and Installation
 

requirements.txt

@@ -1 +1 @@
-lxml>=3.7.3
+lxml>=4.1.1

setup.py

@@ -37,7 +37,7 @@ def _read(name):
     packages=find_packages(exclude=("tests")),
     zip_safe=False,
     install_requires=[
-        "lxml>=3.7.3",
+        "lxml>=4.1.1",
     ],
     extras_require={
     },
@@ -59,7 +59,10 @@ def _read(name):
         'Intended Audience :: Developers',
         'License :: OSI Approved :: Apache Software License',
         'Operating System :: OS Independent',
-        'Programming Language :: Python :: 3.6',
+        'Programming Language :: Python :: 3.7',
+        'Programming Language :: Python :: 3.8',
+        'Programming Language :: Python :: 3.9',
+        'Programming Language :: Python :: 3.10',
         'Topic :: Internet :: WWW/HTTP',
         'Topic :: Software Development',
         'Topic :: Software Development :: Libraries :: Python Modules',