Output the installed version of pip in the build log (heroku#1007)

Since:
* "explicit is better than implicit"
* we'll soon be upgrading pip, and debugging breakage caused by upgrades
  will be easier if versions are visible in the build log

Closes heroku#939.

Author: edmorley

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 # Master
 
+- Output the installed version of pip in the build log (#1007).
 - Reduce the number of environment variables exposed to `bin/{pre,post}_compile` and other subprocesses (#1011)
 
 # 173 (2020-07-21)

bin/steps/python

@@ -150,7 +150,7 @@ fi
 # If a new Python has been installed or Pip isn't up to date:
 if [ "$FRESH_PYTHON" ] || [[ ! $(pip --version) == *$PIP_UPDATE* ]]; then
 
-  puts-step "Installing pip"
+  puts-step "Installing pip ${PIP_UPDATE}"
 
   # Remove old installations.
   rm -fr /app/.heroku/python/lib/python*/site-packages/pip-*

test/run-features

@@ -44,6 +44,7 @@ testStandardRequirements() {
 
 testPipenv() {
   compile "pipenv"
+  assertCaptured "Installing pip 9.0.2"
   assertCapturedSuccess
 }
 

test/run-versions

@@ -9,6 +9,7 @@ testPythonDefault() {
   compile "pythonDefault"
   assertCaptured $DEFAULT_PYTHON_VERSION
   assertNotCaptured "security update"
+  assertCaptured "Installing pip 20.0.2"
   assertCaptured "Installing SQLite3"
   assertCapturedSuccess
 }
@@ -24,6 +25,7 @@ testPython2() {
       assertNotCaptured "python-2-7-eol-faq";
     fi
     assertNotCaptured "security update"
+    assertCaptured "Installing pip 20.0.2"
     assertCaptured "Installing SQLite3"
     assertCapturedSuccess
 }
@@ -51,6 +53,7 @@ testPython3_4() {
   compile "python3_4"
   assertCaptured $LATEST_34
   assertNotCaptured "security update"
+  assertCaptured "Installing pip 19.1.1"
   # if cedar 14 and legacy binaries, fail. if cedar 14 and staging, succeed.
   if [[ ! -n $USE_STAGING_BINARIES ]] && [[ $STACK == "cedar-14" ]]; then
       assertCapturedError
@@ -86,6 +89,7 @@ testPython3_5() {
   compile "python3_5"
   assertCaptured $LATEST_35
   assertNotCaptured "security update"
+  assertCaptured "Installing pip 20.0.2"
   assertCaptured "Installing SQLite3"
   assertCapturedSuccess
 }
@@ -108,6 +112,7 @@ testPython3_6() {
   compile "python3_6"
   assertCaptured $LATEST_36
   assertNotCaptured "security update"
+  assertCaptured "Installing pip 20.0.2"
   assertCaptured "Installing SQLite3"
   assertCapturedSuccess
 }
@@ -134,6 +139,7 @@ testPython3_7() {
   else
     assertNotCaptured "security update"
     assertCaptured $LATEST_37
+    assertCaptured "Installing pip 20.0.2"
     assertCaptured "Installing SQLite3"
     assertCapturedSuccess
   fi
@@ -177,6 +183,7 @@ testPython3_8() {
   else
     assertNotCaptured "security update"
     assertCaptured $LATEST_38
+    assertCaptured "Installing pip 20.0.2"
     assertCaptured "Installing SQLite3"
     assertCapturedSuccess
   fi
@@ -195,6 +202,7 @@ testPypy3_6() {
   else
     assertCaptured "Installing pypy"
     assertCaptured "$PYPY_36"
+    assertCaptured "Installing pip 20.0.2"
     assertCapturedSuccess
   fi
 }
@@ -206,6 +214,7 @@ testPypy2_7() {
   else
     assertCaptured "Installing pypy"
     assertCaptured "$PYPY_27"
+    assertCaptured "Installing pip 20.0.2"
     assertCapturedSuccess
   fi
 }