Update run_*.sh scripts

The Maintainers Guide says that no formatter nor code analyzer
will be involved when you run unit tests, so I suppose
black was added by mistake and should be removed.
Also, using set -e allows you to avoid chaining of commands.

These changes:
  * remove black from run_*_tests.sh scripts
  * add set -e to unchain commands in scripts

scripts/run_integration_tests.sh

@@ -3,22 +3,21 @@
 # all: ./scripts/run_integration_tests.sh
 # single: ./scripts/run_integration_tests.sh integration_tests/web/test_async_web_client.py
 
+set -e
+
 script_dir=`dirname $0`
 cd ${script_dir}/..
 
 test_target="$1"
-python_version=`python --version | awk '{print $2}'`
-pip install -U pip && \
-  pip install -r requirements/testing.txt && \
-  pip install -r requirements/optional.txt && \
+pip install -U pip
+pip install -r requirements/testing.txt \
+  -r requirements/optional.txt
+
+python setup.py codegen
 
-if [[ $test_target != "" ]]
+if [ -n "$test_target" ]
 then
-  black slack_sdk/ slack/ tests/ && \
-    python setup.py codegen && \
-    python setup.py integration_tests --test-target $1
+  python setup.py integration_tests --test-target $test_target
 else
-  black slack_sdk/ slack/ tests/ && \
-    python setup.py codegen && \
-    python setup.py integration_tests
+  python setup.py integration_tests
 fi

scripts/run_unit_tests.sh

@@ -3,22 +3,21 @@
 # all: ./scripts/run_unit_tests.sh
 # single: ./scripts/run_unit_tests.sh tests/slack_sdk_async/web/test_web_client_coverage.py
 
+set -e
+
 script_dir=`dirname $0`
 cd ${script_dir}/..
 
 test_target="$1"
-python_version=`python --version | awk '{print $2}'`
-pip install -U pip && \
-  pip install -r requirements/testing.txt && \
-  pip install -r requirements/optional.txt && \
+pip install -U pip
+pip install -r requirements/testing.txt \
+  -r requirements/optional.txt
+
+python setup.py codegen
 
-if [[ $test_target != "" ]]
+if [ -n "$test_target" ]
 then
-  black slack_sdk/ slack/ tests/ && \
-    python setup.py codegen && \
-    python setup.py unit_tests --test-target $1
+  python setup.py unit_tests --test-target $test_target
 else
-  black slack_sdk/ slack/ tests/ && \
-    python setup.py codegen && \
-    python setup.py unit_tests
+  python setup.py unit_tests
 fi

scripts/run_validation.sh

@@ -1,11 +1,17 @@
 #!/bin/bash
 # ./scripts/run_validation.sh
 
+set -e
+
 script_dir=`dirname $0`
 cd ${script_dir}/..
-pip install -U pip && \
-  pip install -r requirements/testing.txt && \
-  pip install -r requirements/optional.txt && \
-  black slack_sdk/ slack/ tests/ integration_tests/ && \
-  python setup.py codegen && \
-  python setup.py validate
+pip install -U pip
+pip install -r requirements/testing.txt \
+  -r requirements/optional.txt
+
+black --check tests/ integration_tests/
+# TODO: resolve linting errors for tests
+# flake8 tests/ integration_tests/
+
+python setup.py codegen
+python setup.py validate